Solar Energy Perspectives - IEA

Solar Energy Perspectives: Buildings
Solar-assisted reversible heat pumps, combined with better insulation, can considerably
reduce the need for burning fuel in houses and flats. This has been seen recently in
Norway, where more than 30% of detached dwellings have been equipped with heat
pumps in the last ten years, contributing to a halving of heating oil consumption in the
residential sector. But such combinations still consume more electricity than pure solar
systems. Increased electricity consumption is not necessarily an issue, if its generation is
almost entirely renewable, as in Norway with hydro power, or becomes predominantly
solar.
Zero-net and positive energy buildings
Traditionally, buildings have been considered energy consumers; it is now widely recognised
that they can be energy producers. Building envelopes offer considerable surface areas to
sunshine. The European PV Industry Association (EPIA) calculates that “with a total ground
floor area over 22 000 km 2 , 40% of all building roofs and 15% of all facades in EU 27 are
suited for PV applications.” Over 1 500 GWp of PV could technically be installed in Europe,
which would generate annually about 1 400 TWh, representing 40% of the total electricity
demand by 2020. In built-up areas, PV systems can be mounted on roofs (known as
building-adapted PV systems, BAPV) or integrated into the roof or building facade (known
as building-integrated PV systems, or BIPV). Most solar PV systems are installed on homes
and businesses in developed areas. By connecting the building to the local electricity
network, owners can feed clean energy back into the grid, selling their surplus energy to
help recoup investment costs. When solar energy is not available, electricity can be drawn
from the grid.
The IEA Technology Roadmap: Solar Photovoltaic Energy foresees that more than half the
global PV capacity from now to 2050 will be installed on buildings in the residential and
commercial sectors, producing a little less than half the total PV electricity needed
(IEA, 2010c).
Modern PV systems are not restricted to square and flat panel arrays. They can be curved,
flexible and shaped to the building’s design. Innovative architects and engineers are
constantly finding new ways to integrate PV into their designs, creating buildings that are
dynamic and beautiful and that provide free, clean energy throughout their life. Manufacturers
are also beginning to mass-produce elements of building envelopes that integrate PV, or solar
thermal, such as tiles or pre-manufactured units (Photo 4.5).
On a smaller scale, research and experiments have investigated how to integrate CSP in
buildings; a new wave of development may emerge if non-concentrating solar thermal
technologies with thermal storage proves to be a workable option.
According to EPIA, 20 m 2 PV systems in a sunny region (global irradiance at least
1 200 kWh/m 2 /y) would produce enough electricity to fulfil the specific electricity needs
of a family of two to three people for a year, with an excess in spring and summer, and
a deficit in winter (Figure 4.10). This is one approach to the concept of zero-net energy
buildings, or even positive energy buildings; i.e. very efficient buildings able to produce,
from their envelope, as much energy as they consume, if not all the time, at least on yearly
average. (The natural warmth of people inside becomes significant at this level of
efficiency.)
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© OECD/IEA, 2011