Solar energy in building design

Flap to control reverse flow at night

All buildings benefit from unplanned gains of solar energy through windows and, to a lesser extent, through the warming of walls and roofs. This is called 'passive solar gain'; for a typical house in the UK it will contribute about 15% of the annual space heating requirements. With 'passive solar design' this can relatively easily and inexpensively be increased to around 30% while increasing the overall degree of comfort and amenity. The main features of such design are to place, so far as is possible, the principal living rooms with their large windows on the south side of the house in the Northern hemisphere, with the cooler areas such as corridors, stairs, cupboards and garages with the minimum of window area arranged to provide a buffer on the north side. Conservatories can also be strategically placed to trap some solar heat in the winter.

The wall of a building can be designed specifically to act as a passive solar collector, in which case it is known as 'solar wall' (Figure 11.16).50 Its construction enables sunlight, after passing through a double-glazed window, to heat the surface of a wall of heavy building blocks that retain the heat and slowly conduct it into the building. A retractable reflective blind can be placed in front of the thermal wall at night or during the summer when heating of the building is not required. A set of residences for 376 students at Strathclyde University in Glasgow in southwest Scotland has been built with a 'solar wall' on its south-facing side. Even under the comparatively unfavourable conditions during winter in Glasgow (the average duration of bright sunshine in January is only just over one hour per day) there is a significant net gain of heat from the wall to the building.

Double-glazed window

Flap to control reverse flow at night

Thermal storage wall

Opening to permit air flow

Figure 11.16 Construction of a 'solar wall', sometimes called a Trombe wall.

States could be generated from the solar energy falling on PV cells over an area of 400 km square or on CSP installations covering a somewhat smaller area. However, at the present time for large-scale electricity provision, neither is competitive in cost with conventional energy sources or with wind energy. Both require sufficient injection of investment for research and development to grow the economies of scale required to bring costs down to acceptable levels. I will address CSP and PV in turn.

Cold piston

Cold piston

Heat out

Figure 11.17 A concentrating solar power (CSP) system for electricity generation, that consists of a solar thermal array of a number of dish-shaped mirrors each focusing radiation on a receiver attached to a Stirling engine (see bottom left) that converts heat into electricity.

Heat out

Figure 11.17 A concentrating solar power (CSP) system for electricity generation, that consists of a solar thermal array of a number of dish-shaped mirrors each focusing radiation on a receiver attached to a Stirling engine (see bottom left) that converts heat into electricity.

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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