GB2586234A - Energy system based on intermittent renewable power sources - Google Patents

Abstract

An energy system is supplied from intermittent external power sources 1, 2. The system comprises an electrical energy storage system and a thermal energy storage system based on a heat pump 4 powered from the external power source and comprising a phase change material changing between liquid and solid. A cooling appliance 3 is powered from the thermal energy storage system in the absence of external power. The system controls the external power sources, the electrical energy storage system, the thermal energy storage system, and the cooling appliance, and provides electrical power at DC outputs 35 or AC outputs 36. The cooling appliance may be a refrigerator with a freezer, or an air conditioner. The external power sources may be a photovoltaic panel or a wind turbine. The power consumed by the electrical and thermal energy systems may be modulated. The electrical energy storage system is typically a chemical battery which may be located in the cooling appliance. The system is particularly suitable for areas with no reliable electrical supply grid.

Description

The problem: Refrigerators may be found in the international market at low prices that depending on size may be as low as $80 for a normal size refrigerator with fridge and freezer compartments. Developing countries very often do not have a reliable grid and often no grid at all. Often these countries are hot countries needing besides lighting means for food preservation and we must find a way to provide them with a viable solution today.

Just to understand the economic problem, minimum yearly wages in these countries may be as low as Bangladesh $224 or Benin $825 or Butan $691 or Burkina Faso $715 or Guinea-Bissau $392 according to littps://en.wikipedia.orglwikilList of minimum wages by country.

Thus the upper limit for the price of a medium characteristics autonomous energy system including a refrigerator all based on renewable energy may be set tentatively at $300 while the maximum price for a full scale autonomous house should not be more than $600.

Typically a medium refrigerator consumes 100W for 6 hours a day but in hot countries the hours may be 12 depending too on insulation conditions and location of the fridge and how many times it is opened and closed, thus it may consume up to 12h x 100W = 1,2KWh. A refrigerator running on a renewable but non steady source must be able of 3-5 days of autonomy depending on the region, that meaning that it should run autonomously without receiving any energy at all for an average of 4 days. The consumption during that period may be as high as -5KWh and if we put also some other secondary consumption it may reach 6KWh / autonomy period.

The actual commercial price for such a lithium ion battery is roughly $220/K1A1 thus $1320 for 6KWh. It is expected that in the following years lithium ion batteries may reach the $100/KWh barrier. Lead acid batteries for the 2,4KWh capacity do cost less e.g. $165 but their effective capacity is half of the nominal one due to the depth of discharge limitation to set at 50% of their nominal capacity in order to prolong their life, so in the long term the above battery should be changed 3 or more times compared to lithium ion that meaning that is not the correct solution for an energy system having a life time of 12 or more years. Lithium ion batteries on the other side suffer from speedy deterioration at full depth of discharge but in our current design the full depth of discharge may be reached only in extreme cases of lack of primary energy source that is a rare occasion. More over batteries may suffer from exposure to high temperatures and that may be a huge problem in some developing countries where extreme temperatures are not unusual.

On the other side the extremely huge investment that has happened on photovoltaic technology resulted in a very low cost energy capturing system using photovoltaics. Sourcing from the intenet gives us that a panel able to power such a fridge and being oversized by 50% is a panel having an output of 1,8KWh per day instead of 1,2KWh that are needed by the refrigerator. As the collection during hot and sunny days happens during more than 6 hours per day a panel of 300W is sufficient for our purposes and such a panel may cost as low as $0,20-0,25/W thus $60-$80.

It must be pointed out that a developing world house may need overall a consumption of 1,6KW/day to 2,0 KWh/day and thus with an autonomy of 4 days we need over 6KWh of power as already said. The above calculations do not take into consideration any air conditioning unit as that would be extremely demanding on power consumption and energy storage. Typically the energy consumed by the refrigerator in a simple low consumption house could account for 60% of the whole consumption.

While the refrigerator may cost $80 and the PV panel $60 the battery pack will cost at least $1320 if it has to support the refrigerator. The overall system may finally cost over $2500 in order to include installation the sales chain R&D and manufacturing gains.

The above pikes may amount to 6 years of wages or moiv making thus the provision of such a household autonomous energy system just an impossible dream for the time being even when battery prices will lower further.

When we source with energy a refrigerator, we need also to source some lighting and some minor electricity means such as phone charging, small batteries charging AA/AAA etc for portable appliances, and small electric appliances as radios and small TVs running on DC or AC as well as portable computers and fans or small kitchen appliances running on AC. A washing machine may be needed too at a later stage.

Description: Our invention, envisions and models such a low cost energy system for developing countries. As already said, the above things aren't possible actually under the conditions depicted unless a lower cost energy storage system is included in the system and an overall philosophy is designed and implemented in order to consume when power is available instead to consume at will as is done in developed countries. The above philosophy is implemented into our energy system.

The following table shows a low but sufficiently consuming household, more specifically the first column shows the kind of appliance the second column the number of these appliances, the third column the power consumed the fourth column the hours of use of the appliance per day, the next column the daily consumption, the next column night consumption according to our scheme the next column the autonomy and need of stored energy # W use/day hours 3 consumption when during lack of renewable energy Autonomy consumption KWh when electric renewable day energy is provided Refrigerator 1 120 9 1,1 1,08 63% 3,8 TV 1 120 2 0,2 0,24 14% 0,24 0,8 bulbs 3 10 5 0,1 0,05 3% 0,05 0,2 phone charger 2 4 4 0,0 0,02 1% 0,02 0,1 radio 1 25 3 0,1 0,08 4% 0,08 0,3 fan and small 50 3 0,2 0,15 9% 0,15 0,5 kitchen 1 appliances various 1000 0,1 0,1 0,10 6% 0,4 (heating water,hair dryer, etc) 1,7 1,71 1,00 0,53 5,99 The refrigerator should never stop to function and the energy system backing it must be extremely reliable and long lasting.

We have to note that besides Afrika were an autonomy of 3-5 days may be totally appropriate, there are instead countries were due to climatic conditions an autonomy of 10 or more days is needed. That would at least double the cost of the battery energy storage system making impossible for those countries to use batteries even if their prices would drop by 2 or more times.

On the other side, when the sun is shining photovoltaics may provide electricity for phone and battery charging and electricity for TV and other small appliances as mixers fans etc. or even a washing machine. The lack of TV when the energy is lacking is not a huge problem while the deterioration of food inside a refrigerator it is.

In order to be able to design and implement an autonomous energy system based on nowadays technologies and the acquiring power of developing world population, the solution is to use at first two technologies for energy storage so the energy from the Sun will be stored in two parts, and secondarily implement inside the energy system a "consume when you have" philosophy, thus differentiate between the importance of the various consuming appliances providing thus electrical sockets of different categories.

The dependence of human activity on whether conditions is something farmers are accustomed too, so the shift and inclusion of the idea into a household energy system will be natural for them.

The two energy storage technologies are: a) A small battery bank having a capacity indicatively of 0,5KWh up to 1,0KWh (roughly costing actually between $100 and $200) and able to control the refrigerator lighting, energy system logic, refrigerator pumps and fans for a tentatively and arbitrarily set 3,5 days of autonomy and able to provide too home lighting for the same days.

The battery bank should provide too secondary electric appliances with some days of autonomy eventually less than the full refrigerator autonomy of 3,5 days (e.g. 1,5 days). The above energy system will be programmed to be able to cut off other electricity consuming parts of the system when the energy stored approaches the energy needed to source the refrigerator electric consumption for the period of guaranteed autonomy. Along with the refrigerator of equal importance may be considered some light consumption lighting appliances of use for home safety and night vision.

b) Avery low cost energy storage system for the 3,8KW11 (or 101KWh depending on country) needed for the fridge cooling system and using a different storing technology. Such an energy battery may be easily implemented by using a cold storage system based on water e.g. having a salt solved in it and being able to provide cooling indicatively at the minimum temperature of -23C or at higher temperatures. Also other phase change materials as known in the literature may be used at will with the advantages therein described. Thus during the day the fridge compressor runs almost continuously until all the salted water mixture becomes totally ice and all the energy needed for the 3,5 days of autonomy is stored there.

Fridge compressors as per a fast check have very low coefficient of performance that is usually 1,3 for the models of 100W, thus the 3,8 electric KWh do correspond to a heat suction of 3,8KWh x 1,3 5KWh.

We do suppose thus the needed cooling capacity of the fridge should be 5KWh for 3,5 days.

The needed water mass to store 5KWh ( inverse energy storage) is -54Kg of water occupying eventually 701 of freezer space.

For fridges of 300L that is a little bit less than 25% of the space available while future fridges may be modified to accommodate more space for the energy storage freezing section at almost no cost.

The above refrigerator may have a directly coupled direct current motor of variable speed in order to modulate the load towards the photovoltaic panels implementing the Maximum Power Point Tracking technology for all the energy system including battery charging, other appliances and cold energy storage section with variable load motor.

While the DC with voltage control is the more direct solution, also AC with frequency speed control may be used but costs may be higher for the electronics required. Both of these solutions are known art and controller motherboards for voltage control may be found on the net at prices as low as less than $1.

The refrigerator should have ventilators or liquid pumps working on the stored energy and sensors and logic to regulate the air flow and/or pumping power according to the required temperature in the fridge. In case the heat pump is formed from a separate motor and refrigeration compressor, then the motor shaft motor may carry a flywheel for short term speed regulation due to temporary insulation changes. The compressor could be too a variable volume compressor but that would carry a much higher cost. Instead of a flywheel, temporary interruptions or variations in the power received from the primary source, may be smoothed by lowering the speed and feeding the motor from the battery too but for a predetermined maximum period because the battery is a scare resource while solar energy is not. We may say that a minimum speed of the motor may be supported using the battery for 120-180 seconds of insulation variation.

After a drop of insulation bellow the limit needed to support the refrigerating compressor for the above set time, the power should be cut off. When a steady insulation is active again ( e.g. 300 seconds of continuous insulation) then the refrigerating compressor may be put back to work.

For the following discussion we will define "energy day-time" the period of day that the system is receiving energy from intermittent power sources ( it may be at night too e.g. when using a wind turbine), while "energy night-time" the period of day that the system does not receive energy (it may be during the day e.g. when no Sun is available).

Regarding the technology of auto defrost, we have to think and eventually make some modifications. As said the fridge motor runs typically for half a day while for the rest half runs on stored cold "energy". Depending on disposition and implementation, that may mean that a self defrost function is already inherent in the system and running at roughly 12 hours intervals.

Typically self defrost is done via resistors consuming an important amount of electricity.

While this is not prohibitive when running directly on energy received directly from the Sun, we will describe herein some alternative low consumption solutions: * In case that heat transport inside the refrigerator is implemented via air flow between the energy storage section evaporator and fridge compartment, then: During energy day-time the cooling circuit works in the worst case scenario continuously while during energy night-time: At first the fans circulate air between the inactive evaporator coil that has some ice formed on it and the fridge compartment. This has a double effect, at first to defrost the evaporator coil and secondarily to cool the fridge compartment. ;When the evaporator coil is clean of ice, then the fans do work only between the cold energy storage section and the fridge compartment. ;During working mode a) in case the circulation of air through the evaporator ice is not sufficient to cool the fridge appropriately, then in parallel may be used at the same time also working mode b). ;* In case that heat transport inside the refrigerator is implemented via liquid flow and appropriate heat exchangers replacing the evaporator, then: During energy day-time the fridge compartment is cooled by a heat exchanger where liquid typically at temperatures bellow -10C circulates intermittently inside it and transfers cooling power between the cold storage deposit and the fridge compartment. On the above heat exchanger brine may be formed and should be melted at regular intervals.

The above heat exchanger when having a coupled fan, may be defrozen at regular intervals by the fan activating it as in the previously described case.

During the "defrost" working mode of the fan no liquid circulation inside the heat exchanger should happen. Alternatively or additionally if that is not sufficient, the liquid circuit connecting the cold storage section to the refrigerator compartment, may be furnished additionally with an external heat exchanger where the same liquid instead of flowing between the cold energy storage section and the fridge compartment, will flow between a small heat exchanger outside the refrigerator and the the heat exchanger inside the fridge compartment. A liquid valve having 2 positions and 2 ways will be sufficient to divert the flow at will. The fan should be inactive during defrosting in order to avoid unnecessary heating of the compartment. In case the energy system has also access to hot water, then the same defrosting may be done by circulating that hot water in the internal heat exchanger. The hot water may be collected via solar panels or via hybrid thermal-photovoltaic panels or via any suitable method. The difficult side is to find a way to stop the defrosting session as soon as the heat exchanger has been totally defrost.

While the above described energy system may be enough for developing countries, we forgot to mention an improvement that could make the whole system much more advanced and cost effective.

Cooling appliances have three kind of dispositions: a) The refrigerator has it's heating side outside itself but inside the space where the refrigerator is located.

b) The refrigerator has it's heating side outside the space where the refrigerator is located.

c) The refrigerator has it's heating side on the back of the fridge that is located outside the building while the rest of the fridge is located in the inside part of the building.

d) The refrigerator has it's heating side on the back of the of it but has two ducts to suck air from outside the house and expel the heated air outside.

Solution b) is mostly found in commercial or industrial cooling units, solution c) is found in some compact A/C units that are installed trough the wall, solution a) is found in domestic fridges.

Solution a) has the disadvantage that heats up the space where the fridge is located and heats it up mostly when the door is left open and the fridge works continuously.

Solutions b) c) and d) cool the ambient the internal ambient where the fridge is located.

It must be reminded that a normal refrigerator may be made to behave as in cases b) and c) by creating a closed space around the condenser usually located on the back of the refrigerator and creating a natural or forced air flow that sucks air from the outside of the house through a hole in the walls of the house located in the down part and expelling the air heated from the condenser from another hole at a higher location.

By selecting solutions b) or c) or d) for the cooling unit of the refrigerator and over sizing a little bit the compressor of the refrigerator and the cold energy storage section too, we may have with minor adaptations an all in one fridge and air conditioning unit.

Regarding cooling this may be made in two different ways: When fans circulate air or liquid between the fridge compartment and the cold energy storage section then the fridge compartment is cooled.

When instead air is circulated between the cold energy storage section and the space inside the house hold, the ambient were the refrigerator is located is cooled.

The problem with the air flow solution is that contaminants from the external ambient may enter the fridge. This is any way true when the fridge is opened and closed, but the steady and continuous ventilation may accumulate dust and thus we have to provide for a good air filtering section. Instead of having an air hireling section, two different air circuits may be used totally separated while the heat between the two sides may happen by conduction, but overall is not felt as cost effective and practical.

The liquid flow heat exchanger instead solves all that problems in the best way and is the preferred solution. In that case the energy system works besides electricity and refrigeration provides also ambient cooling. In case the energy system has too availability of hot water, then the system may also provide heating, in that case liquid valves should be used again.

Obviously the unification between fridge and A/C is possible and needed for a small size house that does not need huge power and considering the strict budget limits that we have for developing countries. This may be the case of developing world houses being one room or two room houses. The unification allows to use the same energy storage system (eventually over dimensioned) in order to consume energy when available and store it as cold (negative) energy.

lo be noted that the cost to implement the AC cooling side is limited to the blower and heat exchanger that would add a cost of $30-$40 to the system plus should be accounted the costs for overdimensioning of the PV panels and heat storage section.

Using the above methods, we are able to economize at least $1000 of chemical battery for energy storage while having the availability of cooling 2411/24h with an autonomy of 3,5 days at least.

Thus the cost of the house energy system should be something like: a) refrigerator enclosure $80 b) Photovoltaic panel $60 c) Energy storage vessel, antifreeze liquid and ice bricks $20 d) extra fans or pumps $10 e) Energy storage battery $110-$220 depending on technology and capacity.

0 Control logic, pumps charger, conversion to battery and mobile phone chargers etc. $80 Optionally the blower and heat exchanger for A/C. Total: $360-$470.

The above price is the price of a normal self defrost fridge sold in developed countries, while in our case the self defrost is included for free as well as the energy source as well as the mobile phone charger, lighting system and light appliances interface and protective circuits and the source of energy too. We do not account for the sales chain, but that may be minimized by the use of charitable foundation channels.

B

As lithium ion chemical batteries are the most prominent and promising technology but do suffer from fast deterioration when exposed to the high temperatures easily found in hot countries, we should provide inside the refrigerator a controlled temperature region matched against the optimal temperature required for these batteries allowing thus at least a double period of life for them. A temperature sensor along with the fridge logic is sufficient for that. This as simple as it may seem is a tremendous improvement in terms of costs and reliability.

The above region for safety reasons, should be hermetically sealed in no way being able to mix air inside the electronics section with the air inside the refrigerator Heat transport should happen via heat conducting walls of the enclosure of the battery and energy system electronics (e.g. aluminium housing). The above container should be large enough to accommodate a second battery bank in order to increase the autonomy in the next 7 years when batteries will continue to lower their prices, so the system will increase the autonomy to 4 or 5 days.

The energy system does provide also preferably protected (fused or electronically protected) direct electricity current plugs of different power and eventually voltage and AC plugs, these plugs may be attached on the fridge: a) Some power plugs run only when the system receives power from the renewable energy section.

b) Some power plugs of are able to lower or stop the consumption of the heat pump, depending on their required consumption. On these plugs may be connected e.g. a washing machine ( without heating elements) that could eventually need almost all the power of the system for the time that it runs So under conditions of good standing latent heat storage the heat pump may be automatically shut off or it's consumption lowered to the required level for the time that the washing machine is working. The same washing machine consumption depending on motor speed may be modulated depending on needs and maximum power point tracking.

c) Some power plugs take precedence over the refrigerator consumption cause these power emergency lighting appliances or emergency telecommunication equipment.

d) Some power plugs work both on direct renewable energy or on electrically stored energy but do provide energy under the condition to have enough electric energy to power the refrigerator and emergency lighting appliances for the defined and guaranteed autonomy period remaining. So these plugs are disabled when the power remaining in the battery is just sufficient for the autonomy period.

e) Some high voltage DC power connections may exist that are used to share excess external energy to other households having, allowing thus a mesh of households having the same energy system to connect together and share excess energy that would otherwise go lost, or under conditions to share too stored electric energy. These power connections for safety reasons, should be male on the energy system and female on the cable, and protected from access, or could be screw connections where the cable is directly connected. The exact sharing logic can be modelled at will, eventually including some metering that in our opinion is felt as unnecessary.

As already said, some of the above plugs, may be provide AC current output in order to accommodate legacy equipment Ideally the system should provide a sufficient number of plugs and voltages in order to accommodate typical appliances needing DC voltage. Actually DC DC conversion is easily and cost effectively implemented so the above system may provide many plugs with programmable voltages for the output with a very low cost over all.

The above different plug functions may be easily implemented and programmed via a low cost microprocessor controlling the whole energy system logic and once the logic is defined their implementation is just known art.

Depending on costs and efficiency considerations the whole system could be designed too as an AC system using speed control via frequency adaptation for the refrigerator compressor and/or the washing machine motor, and the same logic for the rest of the plugs where some plugs do work only when sufficient renewable energy is received, some others when the battery level is sufficient to guarantee the autonomy of the refrigerator, and some others do work always in order to provide power for the control logic and lighting and emergency telecommunication equipment.

As we are implementing an energy system, the old dilemma between DC and AC will continue to exist and we are totally unable to solve it in our application. So the implementation will just attempt to solve some of the questions and experience will solve the rest along with time.

Departing all the plugs from the energy system housed in the refrigerator, these may be easily controlled by a wi-fr remote control, a radio remote control, an infrared remote control, by a mobile phone having an infrared remote control, or by other known means as voice recognition, thus limiting the necessity of electrical switches.

The simplicity and small size of developing world households, does allow to power all the house with some direct cables departing from the energy system and arriving to appliances without necessitating of an electrical installation inside the house.

The above invention as a whole does create a complete enough self contained and simple solution for a household in developing countries at the necessary price.

Novelty claims: While the whole application has been thought and evolved without review of existing art, it has been found that many similar applications do exist and have similar scope.

We will thus try here to individuate what is novel and what is not.

Including the ice energy storage permanently inside the fridge is not a novelty as may be shown 1. US 6,253,563 El. The above application describes a refrigerator with photovoltaic panel and a phase change material preferably water and glycol, having an opportune load controller in order to maximize the energy extracted from photovoltaic panels and a short term (seconds) energy storage system in order to smooth the power produced by the photovoltaic panels and using it for motor start up.

2. US 7,543,455 B1. The above application, describes a refrigerator based on photovoltaics with a thermal energy storage system based on a special mixture between glycerine water and alcohol that allows for a smooth freezing and unfreezing process that does not create pressure on the container during volume variation. A power source in form of a rechargeable battery is envisioned, but no mention to the recharge method and or connection to the photovoltaics is done.

3. GB2010/051129. The above application main claim requires the water reservoir being higher than the payload container in order to allow natural circulation of water due to the lowest density of water being at 4C. The main novelty being to provide a solution for the natural circulation cause of the lack of a secondary energy source.

4. CN101865586B. The above application describes a refrigerator with photovoltaic panel and battery with controller included in the refrigerator, as well as cold energy storage system all in one, the battery being used just as an additional source of energy for the refrigerator.

From the review of the above applications, it is clear that the above applications do use the thermal phase change method for the storage of renewable energy, do use a controller for optimizing energy extraction from photovoltaics, do use a battery bank too included in the refrigerator.

Our application has developed from a different perspective: provide a complete energy system to developing countries and being thus an all in one autonomous energy system.

It seems thus that the all in one nature of the proposed system is what is novel and what is able to lower the costs of the over all system by including in the electronics all the logic of the electrification of a household. That vision enters and modifies the practical implementation of the whole energy system and makes it different from previous applications, as only by integration and control relinquishment to a single point of control the system starts to become a smart system able to reduce costs and increase efficiency.

It may seem that the most nearby application is CN101865586B but that may not be true while the differences with our system are important: CN10186558613 uses the battery as an additional source of energy to power the compressor motor. Instead we never use energy from the battery to steadily power the compressor motor as the battery is a scarce and costly resource while if we need to provide increased cooling autonomy we have just to increase our cold energy deposit that caries a very low cost over all.

CN101865586B includes the battery and controller including it in the refrigerator, but that is done only in order to have an elegant and practical installation, instead we include the battery and eventually electronics in a temperature controlled region of the refrigerator in order to increase the life of the battery under the specific temperature conditions needed by the battery.

Comparing with US 6,253,563 B1 its claim 7 regulates the speed of the motor in order to do the so called "maximum power point tracking" MPPT.

Our system is a different system with more loads as the the heat pump, the battery bank and other appliances. So the tracking must be done taking into account the variable power loads and fixed power loads ( variable power are e.g. the heat pump, the battery bank but also eventually other loads that may be varied or signalled as adaptable to variable power e.g. washing machine).

While the scope is to track the maximum power point of the Photovoltaic panels, the way to do it with 2 or more variable loads is different, especially when the battery bank is a priority resource before the cold energy storage. Moreover while the battery bank may be a load and be subjected to charging power also when the power received from the intermittent power sources is very feeble, the same isn't true for the heat pump that needs a minimum power in order to run, plus eventually a start up additional power that we may eventually borrow from the battery for some seconds. So the control logic is different and needs more detail and specifications.

More over, eventually having to do with a multiplicity of intermittent power sources, besides photovoltaic panels, also a wind turbine may be optimally loaded in order to extract the maximum power from it's rotation. So the over all logic is more intricate in our system while the optimization scope is the same. Comparing with US 7,543,455 B1 it focuses on the mixture between water glycerine and alcohol creating a special mixture that allows for low expansion during freezing. Uses too a liquid brine as we propose too in order to transfer heat using liquid pumps. The application uses too a rechargeable battery to power the auxiliaries.

The novelty in our system thus seems to be the design of the system as an energy system and not as a refrigerator, with the provision of different kinds of electric sockets at different voltages and working at different times, implementing the "consume when it is free" paradigm into the centre of house electrification". The system also implements the division of power sockets between "emergency ones", "day and night time", "day time only" while all DC sockets may be regulated in DC voltage either automatically (recognizing the plug inserted) either statically, other plugs may provide too AC at a predefined voltage and frequency.

Despite the inventor's living in a 220V region, for developing countries, for safety reasons taking into account the current unawareness of electricity dangers among the population of non electrified regions of the world, and taking into consideration that cable lengths in a typical household will be any way very short, we would firmly suggest 110V AC split as -55V AC and +55V AC.

In our system the priority is set between battery bank charging when the power is too low for refrigeration compressor run, and priority between battery charging and cold reservoir charging, as well as shut off of energy storage when "day time" full power appliances are run (e.g. washing machine or microwave oven). As already said, being an all in one system, maximum point power tracking for photovoltaic panels may be implemented by the load variation of the energy system as a whole where some of the possible variable loads are the battery charger and the heat pump.

In order to define exactly our application, it is not necessary to describe the exact logic that controls the whole energy system, as many possible variations are obvious to the knowledgeable in the art, once the important parameters are pointed out, and the main guidelines evidenced.

The above logic, is any way a software program that will have to evolve in time, along the evidenced guidelines.

The system implements too the division of stored electric energy in "reserve for the necessary period of autonomy of critical appliances" and "energy available for any low power use".

In precise terms, this means that we have to define the 111111111711171 essential energy consuming appliances These may be: a) Telecommunication ( for safety purposes) -e.g. mobile phone recharging b) Emergency lighting -e.g. night emergency lamp c) Refrigerator auxiliaries d) Emergency socket for medical appliances in case these exist of for other use e) Energy system logic and electronics The refrigerator when off power consumes only electricity for lighting when it is opened and for fans or liquid pumps regarding the forced circulation of cooling from the cold energy storage to the freezer and fudge compartments (unless a heat pipe solution is chosen) while usually included in it and consuming electricity are too all the electronics and logic of the whole energy system.

Once a guaranteed autonomy period is set for the refrigerator and emergency appliances (lights, safety equipment as telecommunication equipment etc), then a quantity of energy is determined that is needed in order to power the above equipment for the set autonomy period.

Ideally the above period should be determined and set in a way that depending on the region and climatic conditions as insulation and temperatures, the system should statistically exhaust the battery no more than once per year. Exhaustion of the battery may mean in that context to prolong it's discharge up to 80% of discharge or up to 90% or 100% depending on the effect that the above depth of discharge may have on the battery life depending too on the number of times that this happens per yea'. The above rate of discharge may also be dynamically regulated taking into consideration via opportune software, the number of previous discharges and their depth in order to control the depth of discharge in such a way as to avoid negative effects to the electric battery life depending on the historical data collected.

So finally, suppose that 60% of the battery capacity is needed in order to provide power to the above appliances for the set autonomy period, then when the battery capacity reaches the 40% of discharge thus is at 60% of charge, then the energy system stops providing electricity to non essential appliances (e.g. TV, radio, kitchen appliances) and provides electricity only for the above described "essential appliances". The approach of the critical point may be signalled by the system to the user in order to allow him to lower unnecessary consumptions when approaching the above limit.

The above automatic adaption of consumptions, allows for a better use of the available energy storage resources and instructs and informs the user on when it is possible to consume more or less creating a culture of "consume when you have, and economize when you don't".

The parallel indicated in the current context, of the same energy storage appliance for two uses (refrigerator and air conditioning all in one) may be novel too, while the inclusion of the electronics and especially battery bank in a temperature controlled region is of high importance and again seems novel.

In our opinion thus the novelty starts when the system is viewed as an all in one system id est as a complete house energy system.

The system includes the renewable energy collection side, that being indifferently a photovoltaic panel a wind turbine both and/or other sources -even an unreliable power grid, the electric energy storage is incorporated inside the cooling apparatus and temperature controlled prolonging as required it's life (in the case that this is applicable due to the selected battery technology), while the logic of the energy system allows for smart plugs providing DC or AC electricity of different power and time slides and eventually voltage. With the correct use of electricity there is no need for huge quantities of energy storage. As an example, there is no need to put on the washing machine if there is no Sun because clothes will not dry fast, it is easy to do it later or another day or eventually when wind is available (remember that even at night with wind clothes do dry fast).

When there is no Sun usually there is no need of air conditioning. Eventually a soft air conditioning may be required at night but the maximum need is when the Sun is fully shinning thus the motor providing air conditioning runs on directly produced and consumed energy.

The whole idea does not limit itself to developing countries because every tech geek would like to buy an energy system that does not need electricity and will run forever for free without too many chemicals and that will light the kitchen and make small appliances like a mixer work.

During 12 years life time, a normal fridge in a developing country would consume 100W 10 hours per day thus 1,2KWIilday 365KWh/year that at a cost of $0,2/K.Wh makes roughly $100/year. Thus when a low cost fridge is bought, every year we have to pay its cost again and again to cover the electricity consumed. The above system carries a cost of a fridge and 3 yean of operation of it but no other future costs (besides battery change every 12 years).

Regarding a possible implementation one of them is indicated in the following paragraphs but many variations may be done once the main philosophy concept and details are grasped by any skilled in the arts involved.

Embodiments of the invention The main focus of the invention is on lowering the cost of the energy system by lowering the required electric energy storage system by adding a cold energy storage system and observing that due to the fact that 60% of the power consumption of a typical developing world house is required in order to power the fridge the above cost cut makes economically affordable to provide a renewable power system to developing countries at low cost. More over we lower the environmental impact due to the toweling of quantities of used polluting chemical batteries, and at the same time we prolong their life with the same effect of toweling their pollutant effect.

The other approach is based on separating the power plugs in different categories, as emergency ones always available, in flexible ones, and in optional ones, thus educating the user to use the energy when available avoiding unnecessary uses in moments where energy isn't available.

If a wind turbine is added to the system, shiny day time is not the only moment when energy is available and the plug lamps may show the relative availability.

The invention embodiments may be extremely different. Here will be shown an embodiment but it must be reminded that the embodiments described are only examples while the main invention is on assembling the puzzle for the scope at hand.

A refrigerator has usually two compartments one for food preservation at temperatures above 0° C and one for food preservation in frozen form at temperatures bellow 00 C. For the rest of our discussion we will call the first compartment "fridge compartment" and the second "freezer compartment" and the whole appliance "refrigerator" (even if refrigerator and fridge are the same word).

A first embodiment is formed by: a) One or more intermittent sources of energy as e.g. a photovoltaic panel or a wind turbine producing electric or mechanical energy or both.

b) A refrigerator having: 1. Eventually a DC motor powered directly or indirectly from the above source of electric energy (could be AC too if speed control is done with variable frequency modulation).

2. A refrigeration compressor powered by the source of energy mechanically (e.g. wind turbine) or electrically and mechanically through the DC motor. The compressor runs only when the source of energy is available an exceptionally for short periods even when there is a temporary shortage in energy from the intermittent power sources. Instead of a refrigeration compressor any other heat pump may be used.

3. If the source of energy is mechanical instead the motor may be reversed in use and be a generator in order to convert mechanical to electric energy.

4. A condenser that allows to the refrigerant to release the heat accumulated during compression outside the refrigerator and preferably outside the household.

5. A cold energy storage compartment inside or aside the refrigerator appliance. The energy storage compartment may be implemented in different ways: The compartment may have rectangular boxes that we will call ice bricks these having a height a little bit smaller than the height of the compartment, having one of the other dimensions almost equal to the depth of the compartment and as width a little bit less than a submultiple of the width of the compartment so that many of these set parallelly between them at a small distance along the width of compartment do fill all the compartment. Between the rectangular boxes is left space in order to allow ventilation to pass though and exchange heat, or the compartment is filled with a non freezing liquid able to heat transfer between the evaporator and the freezer and fridge compartments. So either heat is transferred via air flow or via liquid flow the second being most effective. The ice bricks are filled with a phase change liquid that freezes at a temperature indicatively of -10C or lower. The ice bucks should be able to expand without ruptures in order to allow for volume variation between liquid and solid states.

The evaporator may be immersed in the antifreeze liquid, or may better be located outside the refrigerator having all the heat pump outside the household.

Instead of having an evaporator immersed in the antifreeze liquid, and having the most optimal heat exchange, we may instead have a simpler but less efficient system where the evaporator is in the back of the compartment and the ice bricks exchange heat by the use of a ventilation system near by the evaporator. Due to the huge weight of a long term autonomy cold energy storage system that may weight 50Kg or more (we would prefer to opt for a very long autonomy system weighting up to 100Kg) the safest location for the energy storage system is on the low part of the refrigerator as that location lowers the possibility of a dangerous fell of the refrigerator due to external factors. Moreover the location in the low part does not create natural circulation of air that if uncontrolled could over cool and freeze the fridge compartment. 1 he control logic of the fridge will circulate air or liquid as needed using forced flow circulation under direct control of the system logic.

6. One or both from a fridge and a freezer compartment. In order to cool the fridge compartment, a ventilation system should create an air flow getting air from the upper part of the fridge compartment and directing that hot air in the upper part of the cold storage compartment flowing downwards in between the ice bricks and returning to the lower part of the fridge compartment, the air flow may be regulated as fast in order to disallow to the air to cool too much or steady and slow whereby the air entering the fridge compartment will be eventually too cold. The correct working mode should be controlled using temperature transducers, along the height of the fridge compartment. In case there is a too high gradient of temperature between the low side of the fridge compartment and the high part of it, also the reverse flow direction may be used.

Instead of air flow, liquid pumping flow may be used with opportune heat exchangers in the fridge and freezer compartments the liquid coming from the cold storage compartment passing first from the freezer compartment and after from the fridge compartment. In order to cool the freezer compartment only, a separate circuit with separate motor should be used or the circuit should have a 2 x 2 liquid valve.

7. An electronics logic and battery bank compartment eventually the batteries being of the Li-Ion kind. Examining the chemistry of the above batteries it is shown that these do not loose charge and are not subject to fast deterioration when kept at low temperatures. On the other side when at low temperatures their capacity lowers while when at temperatures bellow 0° C are not chargeable. The optimal temperature compromise seems thus to be somewhere in the region between 5° C and 10° C thus the compartment may be cooled from the air flowing from the upper side of the fridge compartment. In order to allow for leakage from batteries or even explosion without contamination of the fridge and freezer a sealed compartment should be devised allowing heat exchange via the external surface towards the internal. The box containing the electronics and battery may be on the top of the fridge compartment over the fridge compartment door aperture, and closed from all sides except a lateral one accessible from outside the refrigerator and having an insulated sealing door. On that door may be accessible from the outside all the electric plugs of the energy system. Instead of that the lateral side may contain the plugs and the aperture of the compartment may be on the back of the fridge. If needed a fan may be inside the compartment allowing for more heat exchange with the heat transfer walls of the compartment that face towards the fridge compartment.

The power strip mentioned will carry some 5V plugs either usb or normal, that allow to connect and charge mobile phones, some other plugs allow to plug the electric input from the renewable power source (male attachment), some other allow to plug other utilities (e.g. a TV some lighting equipment a ventilator) at one or more DC predetermined voltages ( e.g. 48V), or even having plugs of variable voltage controlled by step up of step down DC voltage converters.

Some of the more power full plugs are active only when the external power source is available and there is eventually a led indicator to signal the situation. Some plugs lower the power or totally stop the refrigeration compressor in order to allow another power consuming utility to work (e.g. the washing machine cannot work in parallel with the refrigeration compressor thus the compressor is stopped -unless the cold energy storage is in reserve state and in that case the compressor will be set to work and the other plug will be off). Eventually one or more plugs allowing for a consumption of pure sine wave AC. The power from the DC renewable power source is used to power the appliances plugged in, to charge the battery bank, via an opportune charge controller included in the energy system logic, and if power is still available or the battery is full the refrigeration compressor is run in order to use the remaining energy in order to fill the cold energy storage deposit.

Description of figures

Figure 1, shows the energy system formed in this case from a photovoltaic panel (11), a wind turbine (2) that are connected to the energy controller housed in the refrigerator (3) through electrical lines (31) and (32) respectively. The refrigerator (3) having between others the fudge compartment (11), the freezer compartment (12) and the energy storage compartment (13) ( note: relative size between (12) and (13) are inaccurate in the image). The refrigerator is connected to a heat pump (4) that cools a heat transfer liquid and circulates it into the cold energy storage compartment (13) trough insulated pipes (28) and (29). The heat pump (4) is powered and controlled through line (33) by the energy controller housed in the electronics and battery compartment located inside the refrigerator (3). The above comparonent has a group of interfaces (30) on the left side. The circle (30) zooms and shows the details of these interfaces that are among other: fuse switches (34) and DC (35) and AC (36) electrical outlets. The energy controller supports the conversion of power received from the intermittent power sources the correct charging of battery, the charging of the cold energy storage section (13), the provision of programmable variable voltage to some or all DC outlets (35) and the provision of AC power to the relative outlets (36) consuming from the primary or secondary power source.

Figure 2, shows a possible implementation of the refrigerator side of the energy system.

The box (10) is formed from insulating material that houses a fridge compartment (11), a freezer compartment (12), a cold energy storage compartment (13), an electronics and battery storage compartment (14). The fridge compartment (11) should have shelves not shown in the image.

The cold energy storage compartment (13) is contained in a heat conducting vessel (20) that contains an antifreeze liquid (21). Immersed in the above liquid (21) are phase change material bricks (23). Over the liquid is left some empty space (22) in order to allow for the expansion of the phase change material bricks without causing overflow of the antifreeze liquid. The cold energy storage compartment (13) is closed from the top with a cover that insulates it from the fridge compartment (11). The antifreeze liquid (21) is used as a cold transfer liquid and is being forcibly circulated through a heat pump outside the refrigerator using for that pipes (28) and (29) that should be insulated in order to avoid heat losses. The freezer compartment (12) is cooled via the heat exchanging walls of the vessel (20) of the cold energy storage compartment (13).

Pipes (24) and (25) and the pump (27) are used to forcibly circulate on demand the antifreeze liquid through the heat exchanger (26) located in the in the fridge compartment (11) in order to keep the fridge compartment as cool as required.

The electronics compartment (14) is hermetically sealed from the fridge compartment while being able to exchange heat with it via heat conducting walls, and contains thus in a temperature controlled region the whole electronics and battery bank of the system. Eventually heat exchange may be regulated on demand using a temperature transducer and a blower housed inside the electronics compartment and controlled by the energy controller.

The electronics compartment (14) carries the plugs (30) for DC and AC connections and the input power from the intermittent power sources.

Claims (1)

1. Claims Claim 1: An energy system supplied from one or more intermittent external power sources and connected to at least two energy storage sections one of them using electric energy storage the another using thermal energy storage in cold form and being based on at least one heat pump powered from the external power sources and a phase change material changing phase from liquid to solid state, the system including a least a cooling appliance powered in absence of external power source primarily from the thermal energy storage, the energy system characterized by being an integrated system haying inputs from the external power source(s), connections to the energy storage sections, and connections to outputs at DC and/or AC voltage, the energy system controlling the external energy sources, controlling the energy storage and retrieval from the energy storage sections, providing power to the outputs at DC and/or AC voltage, and to the cooling appliance, using the external power sources and/or the energy storage sections.Claim 2: Claim 1 where the outputs include at least 2 of the bellow categories: a) Always active b) Active when the electric energy storage section has MOM energy stored than the energy needed for the defined and guaranteed days of remaining autonomy of the system c) Active only when the system receives a predefined minimum level of energy from the primary power source(s).d) Input output in order to share power with other similar systems.Claim 3: Claim 1 where the external energy source or sources are at least one of them loaded in a way to extract the maximum power from it, the variable load being implemented by modulating the power consumed by the variable loads of the system among them being the thermal and electric energy storage sections.Claim 4: The previous claim exchanging "Claim 1" with "Claim 2".Claim 5: The intersection between Claim 2 and 5 where category c) is present and prevails over the heat pump consumption modulating the power consumed by it and the heat pump in order to achieve the maximum power goal.Claim 6: The previous claim where the prevailing happens only when the cold energy storage is full over a predetermined percentage of it's capacity or alternatively when the energy storage is sufficient for at least a predetermined time based on statistics kept by the system.Claim 7: Claim 1 where the energy output section is able to provide at least 2 different DC/AC outputs with different characteristics, eventually some of them being programmable per plug, or automatically determined.Claim 8: The previous claim exchanging "Claim 1" with "Claim 2".Claim 9: Any previous claim where the electric energy storage system is a chemical battery bank. Claim 10: The previous claim where the electric energy storage system is included inside the cooling appliance in a controlled temperature region in order to prolong the chemical battery life according to the battery temperature specifications.Claim 11: Any previous claim where the main electronics of the energy system are housed inside the cooling appliance in a controlled temperature region in order to control the temperature and efficiency of the electronics.Claim 12: Any previous claim where the functions and/or activation and control of plug power of the energy system are controlled also remotely.Claim 13: Any previous claim where the over current protections are electronically controlled and restoration too.Claim 14: Any previous claim where there are two cooling appliances one being a refrigerator having eventually a freezer, the other being a cooling air conditioner.Claim 15: The refrigerating equipment defrost method where outside heat is used in order to defrost the internal heat exchanger.