Solar Heating Principles Used at Wakeham
The Hon. Brenda Carter, a pioneer in the use of solar energy in England, with an early experimental solar-heating system, by the Wakeham pool
The solar heating principles used at Wakeham try to balance cost, energy-efficiency, and aesthetic appeal. Although the building makes use of a classical floor plan, it does so for good engineering reasons; the portico is needed to provide shade in summer. There was thus a happy coincidence between solar design and what was needed to get planning permission from a traditionalist planning authority in an Area of Outstanding Natural Beauty on the edge of a National Park.
The new house (which replaces the former Wakeham, shown above, which burned down in 1969) embodies the basic principles of design for passive solar buildings. The massive slate floor in the atrium captures sunlight in autumn, spring and winter and uses this to pre-heat the air used for ventilation in the rest of the building. In that way, solar energy (weak in the UK outside the summer) is used most effectively, by taking the chill off incoming air. It would be much harder, and much less efficient, to try to use solar energy to get the air to room temperature. The building is very highly insulated, and has little glazing on its north side. Its internal walls are white in order to maximize reflection of sunlight onto the slate floor. Air flow in the building is tightly controlled; incoming air enters via the atrium, and is sucked into the surrounding rooms by solar stack effects and by venturi effects, making use of the very tall chimneys (which also carry ventilation ducts, extracting air from the living rooms). Solar design of the main house was the result of a collaboration between The Hon. Brenda Carter (a pioneer of the use of solar energy in the UK) and an architect with extensive experience of solar energy, Ray Maw. The final architectural design of the house was by Robert Adam .
Solar heating of the swimming pool follows principles drawn directly from Mrs Carter’s published research. Rather than using expensive solar collectors, and seeking to achieve high temperatures on a relatively low volume of water, the system seeks to heat very large volumes of water through relatively low temperature rises. Water is sucked by the normal pool filter from the coldest point (the bottom of the 12-ft deep pool); it is pumped through an (uncovered) shallow black-lined paddling pool whenever the sunlight has made the water in that pool very slightly warmer than the bottom of the deep pool; and it is delivered back to the bottom of the deep pool. In that way, the water being heated always remains close to - or sometimes below - ambient air temperatures. There are thus much lower heat-losses to the air from the collector than would be the case with conventional collectors; energy close to 100% of the radiation falling on the shallow pool is collected and transferred to the water. There is some loss of efficiency because the shallow-pool is none-the-less deep enough for children to swim in; but because no additional equipment is required apart from a differential controller to measure the temperature of the two masses of water, and a motorized valve to divert the water flow into the shallow-pool when required, the cost savings compared to conventional collectors are very considerable. It would be even more efficient not have a paddling pool at all, and simply to divert the filter flow over black plastic resting on a bed of scrap polystyrene - the cost of this form of heating is truly trivial, yet the efficiency of collection is greater than that of most commercially-available solar heating systems.
