House design etc. |
|
Design Progress
Report
30 September 2002
“Resolving
Technological Development Issues for Fuel Cell Applications in Social
Housing”.
Current commercial supply of Hydrogen (H2) is by gas-bottle. Where bulk supplies are required a number of gas-bottles are fixed in a cassette and joined together with a manifold.
A typical installation would be a pair of cassettes, each with 16 gas-bottles. These would be interconnected so that as the first cassette empties it is a simple operation to switch over to the second cassette.
Switching can be automated and a warning signal can be delivered so that a replacement for the empty cassette can be ordered.
The Fuel Cell is a component within a system that make it possible to extract energy from the process of forming pure water (H2O) by combining H2 and Oxygen (O2). As such it is similar to the heating element in a kettle or the piston in an engine.
The specific fuel cell has little bearing on the design of a house, although different fuel cell technologies operate at very different temperatures. For a domestic and static application we have chosen so-called “alkaline” technology that operates at the same sort of temperature as a domestic boiler.
Fuel cells only deliver small amounts of electricity and hot, pure water. A fuel cell system therefore has a “stack” of fuel cells joined in parallel.
The system we have chosen is about the size of a large floor-standing domestic boiler. The fuel cells include some very expensive components and the trials we are performing will be at risk of failure through breakdown.
The fuel cell system comprises the fuel cell stack and control technologies for delivery of H2 and O2, transport of electricity and heat generated and internal circulation of a chemical catalyst.
In addition the H2 store and supply pipes, the primary heating system pipes a battery store and an “inverter” that converts the battery electricity into mains-standard electricity are required.
A secure and accessible enclosure is therefore required for the fuel cell system and this is likely to take the form of a large attached store.
Moving trials from the laboratory to the real world always brings with it a risk of failure. Trials in an occupied home mean that failure could be very inconvenient so a back-up supply of electricity and hot water for heating and washing is essential.
To ensure that the occupants are not inconvenienced, the back-up systems will be kept “on” all the time. Controls will ensure that they are not used unnecessarily.
A standard mains connection will be maintained for the house and a standard, but efficient, gas-fired boiler will also be installed as a back-up.
In order to smooth out the peaks and troughs of demand fro hot water and space heating a larger than usual hot water storage cylinder will be installed.
With the exception of the large hot water cylinder, the back-up system will be identical to those systems normally installed in new houses by the Black Country Housing Group.
The above illustration shows the general arrangement of the rooms in the proposed dwelling for the fuel cell trial. This is annotated to show that higher standards of thermal insulation are to be used, in combination with a managed “passive stack” ventilation system.
The dwelling will be built utilizing locally produced structural steel-frames so that a very high standard of air-tightness can be achieved.
The thermal insulation, managed ventilation and airtight construction minimise the amount of heat needed in the winter.
Other design features, e.g. the insulated fridge space and low-energy lighting are intended to reduce the electrical load as well.
The adoption of steel-frame construction provides the space and easy-access for installing, maintaining and changing the services routes, e.g. hot-water pipes and electrical wiring.
Although the automotive industry is migrating to 48-volt electrics from (12v electrics) there are no domestic appliances available yet that can run on 48v electricity. It is not practical therefore to run the dwelling directly from the 48v battery store. If it were, the high cost and complexity of a special interface with the mains-electricity grid could be avoided.
The steel-frame system does enable a later conversion to 48v systems when they become available.