2338295 A solar h emtrof M aM emt This mvention relates to a controller
and a control system for solar powered fluid or water heating, s.
in the type of heating systern to which this mention relates heat flum ihe sun raises the temperature of a fluid (ly water) in a collector and the aim of the w, stem is to er this heal to stored hot water or other substance held in a tank or suitable contamer, by means of a heat exchan,in systems vbiih conventional controllers, whan beat flum tly-- sun raises the temper of the solar panel collector above the temperature of the tank by a small amount, a controller stai a pump so that some of the heat is h to the w21er in the tank by means of the heal-exch in the tank Eventually the temper of the collector falls and the pump is stopped- The following conditions inherent m currently avmlabL- controllers are addressed by- the present iin"tion:- During g the periods of operation of the pump, it runs continuously and Ihe hottest wWa flom the panel is pushed th the hem exchanger bef g ore much of its had has been extra It then passes d the solar panel which has been cooled b) fpe water, and loses more beat This is an inefficient method of king and a pnon of the beat is lost by, distri- Nition through the T in of being accurately erred via ihe heat exchangger to &c tuiL- 71x water in the beat exchanger and feed pipes is cold relative to the solar collector at the time the pump is swi m so the temperature of the collector tends to be reduced immiediately and the pomp way stop while there is still much of the beat not transferredAlternatively, if the pump, continues running, until there is a very small ternperature difFerence bdNmm the collector and the tank, the available beat c has been waly throug the "m and time has also been lost during which the solar collector could have been beating a volume of w21cr to a uwU temperature differenceOverrunning m this way may also have the consequence of ex-u some of the beat back flum the tank and losing it flum Ibe feed or the solar collector In systems with conventional controllers one of these situations must occur, depending on how the contrdler has been set up and calib Both of these possibilities cause losses m addition to the loss caused by a nuous puffTM When the pump stops, either all the beat flom the collector has been distributed over dr entire system, or some warm water remains and it is a matter of chance wt it happens to be in the had ex An additional em in contional controllers is that temperature is measured by analogue sensors which require a difficult calibration procedure and are susceptible to drift and interference, making- unreliability and performance Rely According to the present invention there is provided a control s) designed to replace existingcontrol systems without modification to the rest of the sy and del a much improved performance. Thus, accor(hfe to the present m%ic there is provided a solar heal er s Yle for a domestic water beating control sy comprism- a pumpedL beat er fluid or w-am, a ciron circuit hming at least one solar collector, a 1 circulating pump and a beat exchanger in thermal co with a secondary domestic hot water or other fluid circulation ci an electrumc digital controller; a solar water heating control system comprising: a pumped primary beat exchange fluid circulation circuit having at 1 one solar cofic, a circulating pump and a beat exchang ger in d contact with a secondary fluid circulation circuit; an electrome digital controller, a first sensor, sensing the temperature of the flow du the or each solar colleetw, and a second se sensing, the tenqx"um of the flow through the secondary, water circulation circuit wherein the electronic digiW controHer controls activation and deactivation of die said cimilating., pump is such that wtm.-n output from the first sensor indicates that bun is available m the solar collector at a]c tenqxzwux for Uer to the heat exchangm, the circulating pump is activated for sent 1 of time to bring this heated circulation fluid into the heat exchanger whew it resis until the controller, sensing g the first and second senw outputs, calculates f beat is avúlable m the solar collector at a suitable temperature for er to the beat exchan,,, the chculating pomp is activ for ent length of time to bring fins heated circulation fluid into the beat exchanger where it rests until the controller, sensing g the first and second se outp^ cales that further beat is aymiable in the solar collector at a suitable temper for er to the beat exchanger According to a second aspect of the invention there is provided a controller as cuMy described and as iglus mi fig 4 or Figures, -31 and 4 of the accom-ing drawingL Preferably, the controller is programmed to restart the pump following a delay time leanied from eadier cycles of operation de on the d Qty of the solar collectors and dw of the primary circulation cw unless the signal ftom. the said first sensor indicates that hem is available in the said sobw eofie- Further preferably the invention mcoes any of the features & m the dependerit claims- The controller software operates the ptunp and measures the characwLsbcs of the system In which it is installed- Over a period of time ftWon is accumulated which it uses to automatically Aust If to make the best use of the umlable solar power Wh= beat is available in the solar panel coflww the hot water 1-5 pumped directly and q to the beat exchanger, theri the pump stops and the hat water is left m the heal exchanger for a time which the controller calculates to give optimum heat U At the end of this period any remaining hot wata is moved forward Ihe beat exchanger and the process is repeated until all the hot water the colle has been Ile controller continually tests and corrects its algonthms so that anS modifications or changes m system characteristics am compensated- It can detect the rate of he of the solar panel so dw the best use 1-5 made of small amounts and amounts of solar power by calculating the best temper diffffmtial to the pump wwk-ing- Temperatures in the system are nwasured Ivy, integrated c "di thermometers which allow er accurapy and reliability and no calibration- Ilve- digital int allows rejection of spurious data by numns of software and malfimetion of a thermometer is reliably detected and indicated- 17he controller can find the volume of heated water available m the 2 solar collector m terms of pumping time and pm is stopped whert the last of it has been moved into the beat exchanger g In this way all of the heated w is used and them is never an overrun to pump cooler water into Ihe heat exchangw The efficiency g ftorn this method of Yawk-m- g is augmented by, the fact dot Ihe collector starts heating the next load of water much sooner than would he the case with a conventional controller The use of a small con m the controller rather don the typical analogue cu makes the controller physically simpler and more reliable. It has no user controls or internal Austments and it can operate flom 24OV AC or I IOV AC or from 12V DC and therefore fits easily into alternative e systems where eJ power is stored in batteries- A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings m which:
Fig 1 shows a simple type of solar powered water heating system m winch a controlling cc is necessary- Fig- 2 shows the same system nwoqn the improved controller Fi& 37 shows a diagram of the improved controller connections to its temperature sensors and the W pump and the pownr supply- FWI 4 shows a c diagram ofthe improved controller- Referring to Fig 1 Ihe secondary, system con of a cold water inlet pipe (1) which feeds into the cold water cistern (2) which in turn is connected to the cylinder (31)- Ilke. cylinder (3) has an outlet at its hi point which leads to the heated w outlet (4) ad an overflow into the cold water cistern (2)- The pn circuit consisis of c heat exchanger (5), c within the cylinder (31 which is connected to the solar collectors (6), cimulator pump (7) and a checkvalve (273). The pn =nil is also connected to an expansion tank (9) winch also acts as a header tank for the pd s The controller (10) detects wten the temperatum of sensor (11) attached. to the solar collectors (6) is higher by some specific amount than the temperature of sensor (12) wu to the heated w31cr storage tank- (33)- It then operates the pump (7) which circulates the heated water d the heal exchuL, (5) until the temperatum diflerence between sensors (11) and (12) has been reduced to some specific amount- Power is supplied to the controller from leads (13)- The checkvalve (8) "mm the thermosyphon ef rect- Referring to Fig. 2, the pri and secondary circuits are the same as in Fig 1 but the controller and sensors have been unp The improved controller (14) (the subject of this Patent Application) mplaces the controller (10) of Fig I- An additional temperature sensor (1 JS) is fitted to the exit pipe of the hem exchangeer (5). The pref on of the sensor 3 (16) is on the side of the cylinder C3) midway between Ihe two connections of the beat exchanger (51 In Fig. 3 is shown an outline of a printed circuit board designed for the ved controller with the positions of the terminal connections needed for connection of the power, the pump and the kmqxra= sensors- It lists the connections to be made for operation with both alternating current and direct current supplM- Ile sensor (11) of Fig 2 provides the signal denoted T 1, and sensors (16) and (15) of Fig 2 pf oside the signals 1-2) and T3 respectively- The improved controller is designed to be built on a sing ,(c printed circuit board which can be fitted inside a plastic box which is int to be. mounted on a wag- There are openings fitted with. cable glands for the cables floni. the temperature sensors, from the electrical power source and flum Ihe elmtnc pump of the heating systemThe circuit includes a ormer suitable for use with mam alternatme cunvit electricity g supplies of 110 or 240 volts- The c can also be confi for use with direct current supplies of flom 9 to 20 volts- There are two fuse Inds to independently protect the uomer and the supply to the s pump 11xe. to the pump is controlled by a relay fitted with a suppresser The cu includes a voltage regulator for as micro controller, the clockoscillator and the cdenmd t=perature sensors. Ilw remaining components we Itgbt-e^ng diodes to indicate the operation of the circuit and se The micro controller device contains a micropo Deessor, its program memory kx with a program, some volatile memory and various perk devices- Fig, 4 provides a circuit diagram of the improved controller.
4 CLAIMS
1. A solar water beating control system compnsing: a ptimped primary beat exchange fluid emulation ckcuit having at 1 one solar col, a curng pump and a heal exchanger m thermal contact with a so fluid circulation circuit; an clecume digital controller, a firm sensor, sensing the temper of the flow, dw the or each sober collector; and a second sensor sensing the tempere of the floa d the secondary water cation c wherein the electronic di controller controls acti-t-aflon and deactivation of the said cuctilating pump is such that when output flum the first sensor indicates that beat is available m the solar collector at a suitable tempemttme for er to the beat exchang the pump is activated for sufficient length of time to bring this heated cimulation fluid into the hem exchanger whew it rests 1 the conrroller sensing the first and second sensor outp^ calcul that fierther beat is available m the solar collector at a suitable tempw for er to the heat exchang 2. A solar -a-aim beating control system as c] in claim 1 -^ 1he controller is programmed to festw the purnp following a delay time learned flom earlier cycles of operation dependent on the d capacity of the solar collectors and that of the pnmary circulation c unless thest fi- om the said first sensor indicates that beat is available in the said solar collector- 3. A solar wwa beating control sy as claimed in claims 1 or 27 wherein the second sensor is posd on the side of an in hot fluid st cylinder midway betw the two connections of the beat exchanger with the cylinder wall- 4. A solar water beating control s as cL in claims 12- or -31 wherein a third sensor se the tempeniture of the flow d the pn circulation c is provided adjacent to and on the downstream side of &c said beat exchanger or beat cxcban.,,.
5. A solar water beating control system as claimed in claim 4 wherein the said controller controls the opeuttion of the said pump m response to s from the said first, second and third sensors.
6- A solar water beating control system as claimed in any, preceding claim wherein the heat exchange fluid m the pn and s= circulation circuits is wzter 7 A solar water healing control system as claimed m any precediiig claim, wherein the corttroller is pny_-n such that the pump is operated so as to Uer heated water from the or each solar panel to the said beat exchanger d the said primary circuit and then to cease cffon to allow the said heated water to er beat d &c said heat exchanger for a 1 of time and then to restart ation so as to U the cooled water m the heal exchanger back- to 1he or each solar coll 8. A solar water heating control system as claimed in claim 3Y wherein openition of the pump is ther rep as prmously churned folloume a penod of beat collection in the or each solar collector.
9- A solar water be control s as claimed in claim in any preceding clann and including a microprocessor control circuit as twreinbefore descriffied and illus in Fig 4 of the accompanying dra-aings 10. A solar -a heating controller as before dmml)ed and as illus in Figs. 3 and 4, or Fig 4 of the accompanying drawings- 11. A solar no, control "em as bereinbefore desml)ed as illus in the accompany ying drawings- (0.