GB2177495A - Hot water system utilising solar energy - Google Patents

Abstract

In a solar heated domestic or commercial hot water system a preselected small volume of water may be circulated through a high level solar collector array (SCA), thereby accelerating temperature rise. In a repetitive process throughout all periods of solar gain, successive small volumes of hot water are discharged into the top of the systems normal gravity-fed main hot water storage vessel (HWSV) and/or into other chosen storage facilities. The system can provide preheated feed into the vessel; avoids the use of separate primary and secondary circuits and the special fluids and heat exchangers associated with same; and can automatically drain the solar collector to avoid frost damage. The system comprises three main elements - a vessel (V); a 3 port automatic diverter valve (3PV) and a pump (P). Suitable thermostatic and other controls, and system interconnections, are required. <IMAGE>

Description

SPECIFICATION Solar output control unit This invention relatestoasolaroutputcontrol unit (SOCU) installed in a solar heating system forwaterin domestic or commercial premises.

Liquidsystemsforthetransferofheatfrom aroof- mounted solar collector array (SCA) into a domestic or commercial hot water system are, above all, concerned with transferring heat gains downwards. Unfortunately, the natural thermosyphonic movement in liquids is upwards. Further, besides frost damage to the SCA having to be contended with in many European climates, the users heat utilisation demand characteristic over 24 hours differs substantially from that of solar insolation, and the demand curve can in fact be almost zero during vacation periods for example.

Specialist Companies of substance, today and for a number of years, offer, and have offered, a variety of solar heating systems in which the following prac- tices are commonplace: a) A separate primary fluid system (pressurised with expansion vessel or otherwise) and the consequential use of a primary/secondary heat exchanger at primary/secondary interfaces.

b) Use of an 'antifreeze' or an 'antifreeze and antiboil fluid ' in the primary system.

c) Reliance on hotwaterservices(HWS)havingto be drawn off before solar heated water can transfer from any preheated water storage device into the normal gravity pressurised hot water storage cylin derorvessel (HWSV). As a result, the potential heat storage capacity of this vessel is often not fully exploited.

d) Provision of a replacement or modified HWSV whereby the usual indirect coil or electric immersion heater used to provide gas, oil or electric energy input, is supplemented by a second indirect coil served by the solar primary system.

The present invention is new and not obvious in that its special features enable solar heated waterto be fed downwards into the top of the aforesaid HWSV. The useful top band of hot water therein has always been exitted upwards and, furthermore, in the absence of such special features, any external fluid connection into this exit pointwill induce undesirable loss of vessel heat at one time or a nother by thermo- syphonic effect upwards.

The basic principle of the invention is to create preselected small parcels of solar heated water, in a preselected uppertemperature band,which isconsidered to be adequately hot, and to inject these periodically into the top of the HWSV as aforesaid, using a vented pipe for this purpose. This contraflow againstthethermosyphonic principle is achieved in thatthe invention produces these parcels with a gravity head positive in relation to the quiescent water level ofthe system from which the HWSV draws its water supply.

Whilst no inventive claim is herein made in respect of the aforementioned practices a), b) and d) not being required, in many cases, when the invention is utilised,the userwill thereby benefit in terms of reduced cost and simplicity.

Furthermore, to the benefit of all, the invention could inspire increased usage abundantsolarener- gy available on this planet in thatthe aforesaid parcels of solar heated water could readily be bifurcated in summer, to additionally serve for example an evaporative-type ofchilleror refrigerator- it being that increased cooling demands rise in summer, in variousways, and it is in summer that solar gains are highest.The recently available evacuatedtubularso- lar collector, with much improved winter output characteristics, could then be used with increased scope viz the SCA currently offered to serve only domestic HWS could then economically be sized in excess of the consumers summer hot water needs - and thereby be able to meet a greater percentage of the con sumerswinter hot water needs.

According to the present invention there is a Solar Output Control Unit (SOCU) which is utilised within a solar heated commercial or domestic hot water system (HWSS) in which the solar collector array (SCA) is at an elevated location such that a pump (P) is requires to passwaterthrough it.

The SOCU to comprise three essential elements, interconnected hydraulically and fitted with suitable thermostatic and other control devices. The three elements are: i) Avessel of restrained dimensions (V), see below ii) Athermostatically controlled divertervalve - herein called three port valve (3PV) - having an inletand two outlets herein designated hot (h) and cold (c).

iii) A pump, automatically controlled and of suitable characteristics, serving to pass water up through the SCA, then down into V or3PV. The SOCU to be located so that its elements, as interconnected, ex tend over height(H)which embracesthe horizontal planes h1 (upper) and h2 (lower) containing the quiescent water levels (maximum and normal minimum) obtaining during normal operation of the cold water supply system (CWSS) from which the HWS including V derive a water supply.

The vessel V is not a high volume preheated water storage tank but, specifically, is designed such that when operating it contains a low volume of water such as will heat up rapidly under peakSCAoutput conditionstherebycausing3PVto makea numberof operations hourly. Each operation of 3PV from mode 'c'to mode 'h' will causethe SOCU to engenderthe transfer of an increment of heated water in a preselected and suitable temperature band outofVand thence, without risk of undesirable adverse thermosyphonic effects, into a preselected storage vessel, or other preselected facility which utilises hot water.

Three specific embodiments of the invention will now be described by way of example with reference to the accompanying drawing in which Figure 1 shows the main elements of a typical hot water installation without solar heating.

Figure2showstheSOCU installed in an existing installation to which solar heating is being added, but where existing connections to the CWSS are desirably left undisturbed. The non return valve NRV is desirable. The 3PV is located between V and P.

Figure 3 shows the SOCU installed in anotherway with 3PV located between the SCA and V. It will be noted that, at all solar gain times, HWS draw-offwill induce preheated feed into the bottom of the HWSV.

In both Figures 2 and 3, some desirablethermostatic sensor points (T) are shown and their routes of influence are shown in dotted lines. In the case ofthe thermostat controlling 3PV, its differential will be seen to influence the time intervals and frequency of 3PVoperating, as also will be swept volume ofVand a percentage bypass across the h and c outlets of 3PV in Figure3.

The system pump P has suitable system performance characteristics and is controlled whereby it will only operate in times of solar heat gain and, further, will be locked out should all system heat demands be satisfied and/orshould mulfunction of 3PV, or other control devices, cause system water temperatures to reach a predetermined maximum limit.

With P shut down, draindown of the SCA occurs, thus preventing risk of frost damage.

The systems are suitably vented (vent) and sized and, desirably, a flow regulator R is located as shown to limitSCAoutputflowand pressure to suitable low values.

The simplicity, small size and ease of installation of the SOCU, comprising V, 3PV and P, all located in close proximity and normally adjacentto the CWSS, can readily be deduced from Figures 2 and 3. This demonstrates the economic benefits claimed forthe invention.

Finally, Figure 4 gives the main elements of a scheme wherebythe SOCU, whilst performing its specified function, can be adapted to hold in V a small reserve ofsolar heated water, wholly at a temperature say up to 65'C-foruse on demand i.e. byenergis- ing valve S to open.

Claims (2)

1. Asolaroutputcontrol unit (SOCU) utilised within a solar heated commercial or domestic hot water services system (HWSS) in which the solar collector array (SCA) is at an elevated location such that a pump (P) is required to pass waterthrough it.

The SOCU to comprise three essential elements, interconnected hydraulically and fitted with suitable thermostatic and other control devices. The three elements are: a) Avessel of restrained dimensions (V), see below.

b) Athermostatically controlled divertervalve herin called three portvalve (3PV) - having an inlet and two outlets herein designated hot (h) and cold (c).

c) A pump, automatically controlled and of suitable characteristics, serving to pass water up through the SCAand down intoVor3PV.

These elements may be arranged to form an integrated unit, or be located apart such that, with inter connections,theyfulfiltheSOCUfunction hereinde- scribed.

The SOCU to be located so that its elements, as interconnected, extend over a height (H) which embraces the horizontal planes hl (upper) and h2 (lower) containing thequiescentwater levels (maximum and normal minimum) obtaining during normal operation ofthe cold water supply system (CWSS) from which the HWSS including V derives its water supply.

The vessel V is not a high volume preheated water storage tank but, specifically, is designed such that when operating itcontainsa lowvolumeofwater such as will heat up rapidly under peakSCAoutput conditions,therebycausing3PVtomakea numberof operations hourly. Each operation of 3from mode 'c' to mode 'h' will cause the SOCU to engenderthe transfer of an increment of heated water in a preselected and suitabletemperature band outofVand thence, without risk of undesirable adverse themosyphonic effects, into a preselected storage vessel, or other preselected facility which utilises hot water.

2. A SOCU substantially as described herein with reference to Figures 1 to 4 of the accompanying drawing, and including, in the case of Figure 4, the obvious simplification whereby3PV may be replaced by a thermostatically controlled 2 portva Ive mounted horizontally at level 1 so asto connectVtothe HWSV vent pipe. The level 2 outfall would then be piped directly to point C.

2. A SOCU substantially as described herein with reference to Figures 1 to 4 of the accompanying drawing.

Amendments to the claims have been filed, and have the following effect: (a) Claims 1 & 2 above have been textuallyamended.

(b) The New textually amended claims have been filed asfollows:

1. Asolaroutputcontrol unit (SOCU) as described herein and utilised within a solar heated commercial or domestic hot water services system (HWSS) in which the solar collector array (SCA) is at an elevated location such that a pump (P) is required to pass water through it. The SOCU and SCAto constitute a lowvolume hydraulic loop whereby successive small parcels of water (drawn from the normal supplytank) may recirculate in the loop and be raised in temperature by the SCA, and then be automatically injected into the top of the normal domestic hot water storage vessel (HWSV) via the vent pipe normally running vertically upwards therefrom.Further, for improved SCA heat-collection efficiency, the SOCU may be connected-in so asto offerthefacility ofsupplyingthe HWSV (at low level) with a preheated feed during solar gain periods whenever hot water services are being utilised. A simple control system offers automatic protection against frost damage (draindown of theSCAwhensolargain ceases) and against "boiling-off" (draindown ofthe SCAshould an excessive watertemperature develop in the loop).

The SOCU to comprise three essential elements, interconnected hydraulically and fitted with suitable thermostatic and other control devices. The three elements are:a) A vessel of restrained dimensions (V), see below.

b) Athermostatically controlled divertervalve- herein called three port valve (3PV)- having an inlet and two outlets herein designated hot (h) and cold (c), except where otherwise provided for by reason of the simplification stated in Claim 2.

c) A pump, automatically controlled and of suitable characteristics, serving to pass water up through the SCAthen down intoVor3PV.

These elements may be arranged to form an integrated unit, or be located apart such that, with inter- connections,theyfulfilltheSOCUfunction herein described.

The SOCU to be located so that its elements, as interconnected, extend over a height (H) which embracesthehorizontal planes hl (upper) and h2 (lower) containing the quiescent water levels (maximum and normal minimum) obtaining during normal operation of the cold water supply system (CWSS) from which the HWSS including V derives its water supply. Figures 2,3 and 4 herewith illustrate the foregoing.

The vessel V is not a high volume preheated water storagetank but, specifically, is designed suchthat when operating it contains a low volume of water such as will heat up rapidly under peak SCA output conditions, thereby causing 3PVto make a number of operations hourly. Each operation of 3PV from mode 'c'to mode'h' will cause the SOCU to engenderthe transfer of an increment of heated water in a preselected and suitabletemperature band outofVand thence, without risk of undesira ble adverse thermosyphonic effects, into the upper (normally dry) portion oftheventpipeofthe HWSV; or into a preselected other system which utilises hot water.

The precise volume and configuration of vessel V to relate to the size and water content of the SCA fitted to each installation in that (a) the response (i.e. rate of temperature increase) of the aforesaid loop will be a function of its total swept volumetric capacity when in operation - which includes part of V; and that (b) the top (unswept) portion of Vwill be sized to suit the volume of 'drain-down' water released when the SCA enters the 'drain-down' mode.