GB2058336A

GB2058336A - Solar energy heater

Info

Publication number: GB2058336A
Application number: GB8020979A
Authority: GB
Original assignee: Centro Ricerche Fiat SCpA
Current assignee: Centro Ricerche Fiat SCpA
Priority date: 1979-09-03
Filing date: 1980-06-26
Publication date: 1981-04-08
Also published as: IT7968754A0; BR8005298A; ES8102666A1; DE8019125U1; ES493389A0; FR2464442A1; JPS5637458A; ZA803919B; DE3026982A1

Abstract

A solar energy heater has a solar energy collector panel (1) with an internal air flow duct connected to a cavity (8) surrounding a water tank (4) for heat exchange therewith and a fan (11) for forced circulation of air through the duct, the cavity (8) having dividing walls which define a flow path over the entire surface of the tank (4). <IMAGE>

Description

SPECIFICATION Solar energy heater The present invention relates to solar energy heaters.

More particularly the invention concerns solar energy heaters of the type comprising at least one solar energy collector panel having an internal air flow duct and air inlet and outlet pipes communicating with said duct, a water tank, means for feeding water to a lower zone of the tank and for withdrawing water from an upper zone of the tank, heat exchanger means associated with the said tank and connected to the inlet and outlet pipes of the solar energy collector panel, said heat exchanger means being adapted to heat the water in the tank by utilizing the heat imparted to the air in the solar energy collector panel, and an electrically powered fan for effecting forced circulation of the air through the internal duct of the solar energy collector panel.

The object of the present invention is to provide an improved solar energy heater of the aforesaid type which is of simple and economic construction.

According to the present invention there is provided a solar energy heater of the type comprising at least one solar energy collector panel having an internal air flow duct and air inlet and outlet pipes communicating with said duct, a water tank, means for feeding water to a lower zone of the tank and for withdrawing water from an upper zone of the tank, heat exchanger means associated with the said tank and connected to the inlet and outlet pipes of the solar energy collector panel, said heat exchanger means being adapted to heat the water in the tank by utilizing the heat imparted to the air in the solar energy collector panel, and an electrically powered fan for effecting a forced circulation of the air through the internal duct of the solar energy collector panel, characterised in that the said heat exchanger means includes an insulating casing which surrounds the water tank and is spaced from the surface of the latter by a cavity around the tank communicating with the said inlet pipe and with the said outlet pipe, and dividing walls within said cavity defining a predetermined air flow path in the cavity between the said outlet pipe and the said inlet pipe.

The present invention affords a means of heat exchange with the water tank which is essentially of simple and economical construction.

Preferably the said tank is a pressure-tested tank, and may be similar in all respects to a normal domestic electric hot water tank.

In a preferred embodiment of the invention the said dividing walls are so arranged that the air flowing from the solar energy collector panel which enters the said cavity first flows over the surface of one half of the tank and then flows over the surface of the other half of the tank. In the case where the water tank and the insulating casing are in the form of coaxial cylindrical bodies, the said dividing walls may comprise two radial baffles which join the outer wall of the tank and the inner wall of the casing, the said baffles lying in a common diametral plane containing the axis of the tank.

Preferably, respective temperature sensors are associated with the solar energy collector panel and with the tank respectively, the temperature sensors being connected to a differential thermostat adapted to initiate operation of the fan when the difference between the temperatures sensed by said sensors exceeds a predetermined level.

The water tank may additionally be provided with an electrical resistance immersion heater for use when the available solar energy is insufficient to heat the water in the tank adequately.

In a preferred embodiment of the present invention, the said inlet pipe and said outlet pipe of the solar energy collector panel are connected to the cavity surrounding the tank through a distributor device provided with a main air inlet and a main air outlet, said distributor device being adapted to connect the said inlet pipe and the said outlet pipe respectively with the said cavity and with the said main inlet and main outlet respectively, so as to enable the direct use of the air heated in the solar energy collector panel as well as the indirect use of the heated air to heat water in the tank.

The invention will be further described, by way of non-limiting example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic sectional view of a first embodiment of a heater according to the present invention; Figure 2 is a cross-section taken along line I1--II in Figure 1, and Figure 3 is a diagrammatic sectional view of a second embodiment of the invention.

The same reference numerals are used throughout the drawings to designate the same or corresponding component parts.

In the drawings, reference numeral 1 shows a solar energy collector panel of known type having an internal air duct through which a flow of air is forced, the panel having an inlet pipe 2 and an outlet pipe 3 communicating with the said internal duct.

A pressure-tested water tank 4, which may be similar in all respects to a normal domestic electric hot water tank, is provided with a feed pipe 5 for supplying water to the lower part of the tank and a pipe 6 for withdrawing water from the upper part of the tank. A casing 7 of thermally insulating material surrounds the tank 4 coaxially and is spaced from the latter by a cavity 8 (Figure 2) which communicates through an inlet port 9 and an outlet port 10 in the bottom of the insulating casing 7 with the air outlet pipe 3 and the air inlet pipe 2 respectively. A suction fan 11, driven by an electric motor 12, is located in the outlet pipe 3 for withdrawing air from the panel 1.

Within the cavity 8 there are arranged two radial baffles 13 which join the outer wall of the tank 4 to the internal wall of the insulating casing 7. The radial baffles 13 lie in a common diametral plane containing the longitudinal axis of tank 4.

The cavity 8 constitutes in effect a heat exchanger means for effecting heat transfer from the solar-heated air withdrawn from the panel 1 to the water in the tank 4.

A differential thermostat 14 which is connected to an electrical supply network 15 has an associated temperature sensor 1 6 located near the air outlet of the collector panel 1 and a temperature sensor 17 located in the lower part of the tank 4. The differential thermostat 14 is connected electrically to the electric motor 12 so as to energise it when the diference between the temperatures sensed by the two temperature sensors 16, 1 7 exceeds a predetermined value.

Within the tank 4 there is arranged an electrical resistance immersion heater 1 8 which is connected to the supply network 1 5 through a manually operable switch 1 9. The heater 1 8 is energised by closing the switch 1 9 when the available solar energy is insufficient to afford adequate heating of the water contained in the tank 4.

The switching on and off of the electric immersion heater 1 8 may also be controlled automatically by the differential thermostat 14.

The solar energy heater illustrated in Figure 1 operates'as follows. When the difference between the temperatures sensed by the temperature sensors 1 6, 17 exceeds the aforesaid predetermined value the differential thermostat 14 switches on the fan motor 23, causing the fan 11 to establish a forced circulation of air through the solar energy collector panel 1. The air heated by solar energy in the collector panel 1 passes into the cavity 8 through the outlet pipe 3 and the inlet pipe 9. The air flows upwardly through the cavity 8 in a longitudinal direction, over the surface of one half of the tank 4.At the upper end of the tank 4 the air flows through the upper part of the cavity 8 between the upper end surface of the tank 4 and the casing 7, and then flows longitudinally downwardly through the cavity 8 in the opposite direction over the surface of the other half of the tank 4. The air flows out of the cavity 8 through the outlet port 10 and re-enters the solar energy collector panel 1 through the inlet pipe 2.

The embodiment shown in Figure 3 differs from that of Figures 1 and 2 only in that the inlet pipe 2 and the outlet pipe 3 of the solar energy collector panel 1 communicate with the ports 10 and 9 respectively through a distributor device 20. The distributor device 20 is identical to that described and illustrated in British Patent Application No. 7920825 filed 14th June, 1979. The distributor device 20 is provided with a main air inlet 21 and a main air outlet 22 and is adapted to connect the pipes 2 and 3 to the inlet 21 and to the outlet 22 respectively as well as to the respective ports 10 and 9.Thus the air leaving the solar heat collector panel 1 through the outlet pipe 3 may be wholly or partly directed, according to the setting of the distributor device 20, into the main outlet 22, so as to enable at least some direct use of the air heated in the solar energy collector panel 1. In the case where some or all of the air flow passes through the outlet 22, a corresponding quantity of air enters the distributor device 20 through the main inlet 21 and flows into the inlet pipe 2 of the solar energy collector panel.

The distributor device 20 enables indirect use to be made of the air heated by the solar energy collector panel 1 to heat the water in tank 4, and, at the same time, enables direct use of a controlled quantity of this heated air.

It will be understood that details of construction of practical embodiments of the invention may be varied widely from what has been described and illustrated by way of example, without thereby departing from the scope of the present invention.

Claims

1. A solar energy heater comprising at least one solar energy collector panel having an internal air flow duct and air inlet and outlet pipes communicating with said duct, a water tank, means for feeding water to a lower zone of the tank and for withdrawing water from an upper zone of the tank, an electrically powered fan for effecting a forced circulation of air through the internal duct of the solar energy collector panel, and heat exchanger means associated with the said tank and connected to the inlet and outlet pipes of the solar energy collector panel, for heating the water in the tank by utilizing the heat imparted to the air in the solar energy collector panel, wherein the heat exchanger means includes an insulating casing which surrounds the water tank and is spaced from the surface of the latter by a cavity around the tank communicating with the said inlet pipe and with the said outlet pipe, and dividing walls within said cavity defining a predetermined air flow path in the cavity between the said outlet pipe and the said inlet pipe.

2. A solar energy heater according to Claim 1, in which the water tank is a pressure-tested tank.

3. A solar energy heater according to Claim 1 or Claim 2, characterised in that the dividing walls are so arranged that the air flowing from the solar energy collector panel which enters the said cavity first flows over the surface of one half of the tank and then flows over the surface of the other half of the tank.

4. A solar energy heater according to Claim 3, in which the water tank and the insulating casing are in the form of coaxial cylindrical bodies, and the said dividing walls comprise two radial baffles which join the wall of tank and the wall of casing, said radial baffles lying in a common diametral plane containing the axis of the tank.

5. A solar energy heater according to any one of the preceding claims, in which respective temperature sensors are associated with the solar energy collector panel and the tank respectively, the temperature sensors being connected to a differential thermostat adapted to initiate operation of the fan when the difference between the temperatures sensed by said sensors exceeds a predetermined level.

6. A solar energy heater according to any one of the preceding claims, in which an electrical resistance immersion heater is associated with water tank and is energisable when the available solar energy is insufficient to heat the water in the tank adequately.

7. A solar energy heater according to any one of the preceding claims, in which the said inlet pipe and the said outlet pipe are connected to the cavity surrounding the tank through a distributor device provided with a main air inlet and a main air outlet, said distributor device being adapted to connect the said inlet pipe and the said outlet pipe respectively with the said cavity and with the said main inlet and main outlet respectively, so as to enable direct use of the air heated in the solar energy collector panel, as well as indirect use of the heated air to heat water in the tank.

8. A solar energy heater substantially as herein described with reference to and as shown in Figures 1 and 2 or Figure 3 of the accompanying drawings.