DE3005553A1 - Control system for bivalent heating plant - using solar and conventional energy with recording and computing unit using temperature gradients as control features - Google Patents

Abstract

The control system is for a bivalent heating plant operated in the storage range for solar energy. The heating plant is also supplied with additional energy. It is intended to maximise the use of the solar energy and to minimise the consumption of the additional energy. The required amount of hot water at an adjustable minimum temperature is guaranteed. The temperatures in the storage ranges are recorded separately at equal regular intervals and the instantaneous temperature gradients determined. The additional energy is supplied at the point of intersection of the two temperatures. The temp. sensors (4,5) supply a signal to a transducer (12) whose electrical signal outputs are supplied to a store (13). The values are evaluated and used to control a function generator (15).

Description

The invention relates to a method for controlling a

bivalent heating system, in particular a storage area for solar energy and for additional energy having heating system and a device for practical Implementation of this procedure.

It is known to use solar systems to generate energy The most sensitive possible temperature difference measurement between the collectors and the Control storage facility.

If the temperature of the collectors is higher than the storage tank temperature, the heat gradient is increased in favor of the storage tank temperature by means of a circulation pump balanced.

In this way, on the one hand, there is a rise in temperature in the heat accumulator causes and on the other hand prevents that when the temperature ratio is reversed Heat is withdrawn from the storage tank, fed to the collectors and radiated there.

It is also well known that with so-called non-conventional Energy, such as solar energy, geothermal energy and / or water heat operated heating systems without additional heating devices operated with so-called conventional energy such as electricity, gas or coal are not able to meet the user's full heating energy needs, so that in practice at least bivalent heating systems are always used, i.e. Systems that use both non-conventional and conventional energy be operated, always trying to use the non-conventional energy, in particular to use the sun's heat optimally, while the respective remaining energy demand an additional heating operated with conventional energy is covered.

It is also already known, a bivalent heating system in the way build that a first, heatable by a solar collector circuit memory and a second storage device, which can be heated up by means of additional energy, is connected in series with the outputs of both memories above connected to a thermal mixing valve are that works in such a way that from the heatable memory with additional energy warmed or heated water is only drawn off when the need for hot water or hot water from the first storage tank assigned to the solar collector circuit more can be covered or the required temperature is no longer reached and therefore an admixture from the second memory must take place.

The object of the present invention is to provide a method for control a storage area for solar energy and a heating system with additional energy to create that makes it easy to implement, while at the same time Maximizing the use of solar energy, minimizing the need for additional energy, always the required provision of heating or hot water of determinable Minimum temperature is to be guaranteed.

This object is achieved according to the invention in that the temperatures of the two memory areas in predeterminable equal time intervals are recorded separately and at the same time and determined from two successively Temperature values the current temperature gradient of each memory area is determined that by determining the point of intersection of the respective temperature gradients those without the use of additional energy until the intersection temperature is reached required system time and with the fixed heating time the additional energy is compared, and that is then dependent on the result this comparison and the result of another comparison between the intersection temperature and a predeterminable minimum temperature in the storage area that can be heated with additional energy the additional heating is switched on.

The basic idea of the method according to the invention can accordingly can be seen in the fact that by constantly following the course of temperatures in the two stores and by evaluating these temperature curves anticipated temperatures in the two storage tanks are taken into account in this way that the additional energy is only used if there is a high probability that or can be foreseen practically with certainty that taking into account the future projected course of the temperatures of the two storage tanks the required minimum water temperature can no longer be guaranteed. Consequently is achieved through targeted observation of the temperature curves of both storage areas and avoiding the continually repeated extrapolation of these temperature profiles into the future, that additional energy is used at a point in time at which due to the forward-looking Assessment of the temperature profile of both memory is already foreseeable that the Storage tanks assigned to solar collectors will soon provide that energy that is required to maintain the specified dispensing temperature level is.

By linking the result of a temperature comparison and the result of a time comparison for the purpose of obtaining a switch-on signal for the auxiliary heating becomes the basis for achieving the according to the invention desired optimum created.

An advantageous variant of the invention consists in that to further increase the savings in additional energy from the respective consumer fixed or typical for him daily, weekly and / or seasonal Requirement is taken into account in such a way that the minimum temperature is dependent is varied by the respective need. In this way it can be achieved that in Time spans, in which the energy requirements of the user of the heating or water heating system Experience has shown that the switch-on criterion is low in favor of a saving of Additional energy is changed, taking into account the consideration that until the point in time at which the demand increases again, there is definitely the possibility of that the required energy can be obtained from the solar circuit.

Further advantageous embodiments of the invention and in particular also an advantageous device for performing the method according to the invention are specified in the subclaims.

The invention is described below with reference to the drawing for example explained in more detail; in the drawing shows: -Fig. 1 a schematic Representation of a bivalent heating system, which according to the method according to the invention is controlled, Fig. 2 is a diagram to explain a possible temperature behavior of the two memories according to FIG. 1, FIG. 3 shows a diagram to explain the determination the intersection temperature with the aid of the temperature gradient, FIG. 4 a decision table, and FIG. 5 is a diagram for explaining the computational determination of for the method according to the invention essential variables.

According to Fig. 1, the solar system explained here as an example includes a Solar storage tank 2 as well as an additional storage tank 1 connected downstream of this, whereby the Output lines of both memory are combined via a thermal mixing valve 3.

There is a temperature sensor 4 in memory 2 and a temperature sensor in memory 1 5 arranged.

The additional memory 1 is equipped with a heating device 6, which in the example shown is an electric heater that has a switch 7 can be switched on. Instead of an electric heater, however, any other form of additional energy, e.g. oil or gas, to heat this storage tank 1 can be used.

In the memory 2, a heat exchanger 10 is arranged, which is in a with a circulation pump 11 equipped solar collector circuit is switched on. One example The solar collector shown is marked with the reference number 9.

The connection of the additional heater 6 in the memory 1 is via an electronic Control device 8 controlled, the structure and mode of operation will be explained.

In Fig. 2 is an example of a possible temperature profile in the two memories 1, 2 shown as it is about in good weather and normal Water consumption in the time from 8 a.m. to 12 noon can result, whereby however, the representation of the curves in the sense of a clearer Explanation are shown spread apart.

It can be seen that the temperature T1 of the heatable via additional energy Memory 1 initially decreases to a predeterminable minimum temperature Tamin, whereupon then the additional heating is switched on and the temperature of storage tank 1 during the heating-up period t is increased to the temperature T lmax, which can again be predetermined.

At the same time it can be seen in this Fig. 2 that the temperature T2 of the store 2, which can be heated by means of solar energy, due to the increasing solar radiation increases and reaches the temperature T1min around 11 o'clock and then even further is increased. In the context of the considerations on which the invention is based It is important that the temperature T2 of the storage tank heated with solar energy the specified minimum temperature relatively short time after the drop in the Temperature T1 reached to the minimum temperature Tlmin, which is synonymous with it is that a further decrease in the temperature in memory 1 at this time of day It could have been taken into Knauf, as it was done within a relatively short period of time already the resulting energy gap due to the then available solar energy can be compensated. Switching on the additional heating and the associated Energy consumption could accordingly be avoided if, for example, the specifiable Minimum temperature T imin corresponding to the curve indicated by dashed lines in FIG T1, min depending on the time of day and thus taking into account consumption habits would be varied.

In the context of the present invention, however, are for the decision other criteria are taken into account with regard to the use of expensive additional energy, and in particular the course of the temperature gradients in the stores 1 and 2. By projecting the current temperature gradient into the immediate one In the future, it should be ensured that the additional heating is only switched on then takes place when all indications suggest that the required minimum temperature T1min before the time t has elapsed, which corresponds to the heating-up time due to additional energy, will not be achieved. The time period t will vary depending on the system and can for example 0.25, 0.5, 0.75 hours or even one Hour.

The time intervals between individual sampling times t1. . . t are significantly shorter than the typical heating-up time for t1, 2n a system t is selected, with the definition of these time intervals both the heating-up time and the precision of the readings is also taken into account to avoid unnecessary Switching or avoiding a strong overshoot. According to a kind of rule of thumb The rule is that longer distances for smaller heating systems and longer distances for larger heating systems shorter intervals can be selected between the individual sampling times.

The principle of taking into account the temperature gradients is based on of Fig. 3 described.

In this example, at fixed intervals of three minutes the specified times t1, t2 t3r. tn the storage tank temperatures T1 and T2 assigned pairs of measured values T1T21, T12 T22 and T13 T23 determined and recorded, so that between the measuring times t1-t2 and t2-t3 in the memories 1 and 2 prevailing temperature gradients can be calculated.

As can be seen from FIG. 3, the pairs of measured values are added to the point in time t2 used to form the triangle T11-T21-T32 entered. T32 is included the target temperature T3 extrapolated from two pairs of measured values, which is expected to be will be reached after a time tX2.

This process is repeated after each sampling cycle, in the present case For example, at time t3, the penultimate pair of measured values T11-T21 is deleted and transferred to its Set the last pair of measured values T12-T22 and use the new pair of measured values T13-T23 the new gradient is calculated or a new triangle T12-T22-T33 is formed will.

The triangles determined have temperature in the coordinate system and time one for the temperature values and in stores 1 and 2 Temperature curves characteristic shape and position and are - as already explained - in each case at the times tn + 1 within the meaning of the present invention for the desired Minimization of the use of additional energy used.

From Fig. 3 it can also be seen how the position and shape of the triangles change after each measurement process depending on the temperature curves T1 and T2 can. It is essential that with constant monitoring of the development of the gradient course the level of the target temperature T3 also changes constantly and thus the actual one Conditions can be taken directly into account in each case.

The temperature level T3 can be higher, lower or equal to the desired one Be the minimum temperature Tmin, and the same applies to the time period tx with respect to the heating-up time t of the additional heating.

Using the table according to FIG. 4, it is shown, for example, in which cases, taking into account the above principles, the additional heating would be switched on.

The minimum temperature is set to Tmin = 500C and that of The heating time t required for the additional heating is assumed to be 0.5 hours.

The table shows the respective combination of expected, i.e. by observing the temperature gradient determined temperature T3 and the time span tx, within which this temperature level T3 is expected to be reached.

First of all, this table immediately shows that one is only about the instantaneous values of the temperatures in the two storage tanks controlled auxiliary heating in any case would be switched on if the temperature was below the specified Minimum temperature Tmin = 500C would drop.

That is, fields F3, F6 and Fg correspond to an on-state became.

In the case of a heating system controlled according to the method according to the invention however, the additional heating would only be switched on in the hatched field F3, since only in this case must it be assumed that it will not succeed solely by means of solar energy within the heating time assumed to be 0.5 hours to reach the specified minimum temperature of 500C. This through observation The knowledge gained from the course of the temperature gradients then also justifies switching on the additional heating.

In field F6 there is an immediate activation of the auxiliary heating before, but it is still dependent on the tendency of t.

The conditions given in field Fg normally do not lead to switching on the additional heating, but depending on the time of the day Minimum temperature Tmin cause a switch-on if - as shown in FIG. 2 indicated is - the minimum temperature is selected to be variable.

It is also possible, depending on the course of the target temperature T3 to determine a gradient and to make a direct decision about switching on the auxiliary heating.

The target temperature describes a locus curve that increases with increasing Temperature in the solar circuit on the one hand in the direction of higher temperatures and on the other hand runs in the direction of smaller times.

It is of particular advantage that the for the implementation of the invention Process essential variables tx and T3, for example using a microcomputer can be determined quickly and easily.

One possibility for determining these variables by linear extrapolation is explained with reference to FIG. 5, it being assumed that the measured values T11, T21; T12, T22 can be recorded every 3 minutes, the temperature scale being shown here as well for a better understanding. With the help of the trigonometric functions the following results for the gradient of memory 1: b tgZ b T11 11 T12 (a) - tg- a 3 min and for the gradient of memory 2 we get c T22 - T21 tgß = a 3 min. b = c tg α tgß c = b.tgß (c) Furthermore, it follows from Fig. 5: b + c = T11 T21 (d) from which it again follows that b + = T "1 ß T21 tg T21 b = T11 - T21 1 + tgF / tgob (e) With the help of equation (c) one obtains: T11 - T21 tgß tc = 1 + tgß / tgα tgα The quantity tx, which corresponds to the previously used quantity a, is thus obtained according to the following equation: T11 - T21 1 tx = 1 + tgß / tgα. Tgα (g) The quantity T3 is determined from: T3 = T11 -b and thus using the equation (e) T11 - T21 T3 = T11 - 1 + tgß / tgα (h) The practical implementation of this Very simple functions by means of a control device using microprocessors can possibly be carried out very cost-effectively with so-called one-chip computers in smaller systems because of the low memory requirements required and, above all, poses no problems in terms of the task at hand a schematic example of such a control device 8 is given.

The data from the temperature sensors 4, 5 in the store 1 and 2 instantaneous temperatures determined via a device 12 for implementation the temperature values are fed into electrical measured values to a measured value memory 13, the times of the measured value memory and the measured value evaluation by a clock 14 controlled are. To determine the quantities T3 and tx, a Function generator 15 also controlled by clock generator 14 is provided. Means a device 16 is a comparison of the intersection temperature T3 and the adjustable Minimum temperature Tmin as well as of tx and additional energy heating time t made. The connection of the additional energy source 6 via the switch 7 then takes place via a logic circuit linking the comparison results.

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Claims (5)

Method and device for controlling a bivalent heating system Claims C1.) Method for controlling a bivalent heating system, in particular a storage area for solar energy and a heating system with additional energy, as a result, the temperatures of the two storage areas recorded separately and simultaneously in predeterminable equal time intervals and the instantaneous temperature values are determined from two successively e; Temperature gradient of each storage area is determined by determining the point of intersection of the respective temperature gradients without the use of additional energy The system time required to reach the intersection temperature is determined and is compared with the fixed pre-set heating time by the additional energy, and that then depending on the result of this comparison and the result of another Comparison between the intersection temperature and a specifiable minimum temperature The additional heating is switched on in the storage area that can be heated with additional energy will. 2. The method according to claim 1, characterized in that g e k e n n -z e i c h n e t that the additional heating is only switched on if the system time greater than the additional energy heating time and at the same time the intersection temperature is lower than the minimum temperature. 3. The method according to claim 1 or 2, characterized in that g e k e n n -z e i c h n e t that the minimum temperature depends on the season, time of day and / or Outside temperature can be changed. 4. Device for carrying out the method according to one or more of claims 1 to 3 using a heating system with a solar collector heatable first memory, one heatable by means of additional energy and with the first memory connected to the second memory and one to the outputs of the two Storage connected thermal mixing valve and one arranged in each storage tank Temperature sensor, marked by the fact that the temperature sensor (4, 5) via a device (12) for converting the temperature values into electrical ones Measured values are connected to a measured value memory (13) that the times of the measured value storage and measured value evaluation are controlled by a clock generator (14) that for measured value evaluation on the temperature gradients of the two stores (1, 2), the intersection temperature (T3) and the respective system time (tx) determining function generator (15) is provided is that this function generator (15) a device (16) for Comparison of intersection temperature (T3) and adjustable minimum temperature (Tmin) as well as system time (tx) and heating time (t) is assigned by additional energy, and that the connection is made via a logic circuit that links the comparison results the additional energy source (6) is controlled. 5. Apparatus according to claim 4, characterized in that g e k e n n -z e i c h n e t that the logic circuit is followed by a threshold device, their working point possibly together with the working point of the function generator in Controllable depending on a year / time of day or outside temperature dependent transmitter is.