We are getting closer to having all the pieces in place for zero carbon homes – cost-effective solar power, good insulation and materials, heat recovery, improving energy storage – but they aren’t all there yet. We still need better ways of storing solar energy locally to keep systems running in the winter. And there is the issue of how much CO2 is released in manufacturing the building materials and the construction process itself – which together can be as much as 20%-50% of the whole life carbon footprint of the home.
In 2015, the Welsh School of Architecture, based at Cardiff University, designed and built a highly innovative low-carbon home which brought together many of the pieces. Costing around £1,000 per square metre to build, it is within the budget allowed for housing association homes, making it an entirely practical solution rather than a ‘concept’ home.
The property, near Bridgend, has insulated render on the outside plus glazed solar photo-voltaic (PV) panels fitted into the south-facing roof, allowing the space below to be naturally lit.
The house uses solar generation and battery storage to run both the combined heating, ventilation and hot water system, and the electrical power system, which includes appliances, LED lighting and a heat pump. The solar air system preheats the ventilation air, which is also warmed by a warm water store.
Energy from the national grid is still needed during the winter but then even more energy is exported and sold back to the grid during the summer months. This sounds great if you are the home-owner but from a sustainability point of view, this where we have a missing piece in the puzzle.
The more low-carbon homes are built the more demand there will be for the top-up energy in winter – but if this national grid winter energy is not low-carbon then the overall sustainability benefits start to dwindle. So how can we create more low-carbon energy in winter? Wind turbines, powered by winter storms, seem an obvious option, along with biomass boilers which at least keep carbon emissions neutral.
At a local area level greater use of hydrogen-cells may be a storage option for summer solar energy, as long as the hydrogen itself is also created with clean energy. Hydrogen cell storage, however, does present some technical and cost issues at a large scale.
Solar hydrogen homes in Thailand
An exciting low-carbon housing development in Thailand uses solar power to create the hydrogen used in hydrogen storage cells. These are then used as a more efficient long-term energy store alongside short-burst energy supplied by solar-charged batteries. The fact that this development is in Thailand clearly helps with greater year-round sunshine but it is still an interesting way forward.
Note from Editor – Ian Glennie
- I will be interviewing architects and housing associations in the UK on their ideas and plans for low-carbon (and one day zero-carbon) homes – so check back here soon or sign up for our updates.