Energy System
How does it work?
As you can see in the diagram below, the energy system comprises a number of components:
Wind Turbine
The wind turbine will produce enough electricity to power the Hydrogen Office, produce hydrogen for the fuel cell (see below), meet the needs of ongoing research and development, and for much of the year will produce enough surplus to sell to the national grid. It will prevent about 774 tonnes of CO2 emissions each year which equates to a ‘payback’ time for the carbon dioxide emissions relating to the construction of the Hydrogen Office and wind turbine of 19 to 37 months (depending on the final size of turbine used and wind speeds on site).
Fuel Cell
By passing an electric current through ordinary tap water, the water molecules separate into the hydrogen and oxygen atoms they are made of. The process is called electrolysis. The Hydrogen Office will use electricity produced by a wind turbine to do this. Oxygen gas, produced at the anode, will be vented off to the atmosphere, whilst hydrogen gas, produced at the cathode, will be fed to a tank.Hydrogen Storage and Use
A specially designed tank will store about 30 kgs of hydrogen gas, under a moderate pressure.
The wind turbine wil provide the electricity for the building when it is turning, but when the wind drops, a fuel cell will automatically switch on to maintain the electricity supply to the Hydrogen Office.
When the fuel cell is 'switched on', hydrogen is fed into the fuel cell, which generates electricity by the reverse process of electrolysis - combining free hydrogen and oxygen atoms to make water, and producing electricity as a by-product. The resulting water is pure, and will be safely drained into the normal sewage system. No greenhouse gases are produced at any stage of the process.
The aim of the project is to demonstrate, and further develop, the use of hydrogen storage to buffer the intermittency of wind power, which is otherwise at the mercy of nature.
Domestic Hot Water
In addition to providing electricity, the fuel cell will also be used to heat water for the domestic hot water supply for the Hydrogen Office.
Ground Source Heat Pump (GSHP)
No matter how much the temperature changes on land, the temperature even just a few metres below the ground remains constant. By drilling boreholes to a depth at which the rocks are approximately 12oC all year round, water for the heating system can be pumped down, be warmed by the surrounding rocks, and then used to heat the Hydrogen Office. The system is very efficient: by using a GSHP, every unit of electricity used by the system will generate 4 or 6 times that of heat!
The water isn't used to heat the building directly: instead, the heat is extracted from the water by a system similar to your fridge at home. Just as the inside of your fridge stays cool, and the back gets warm, so the water in the borehole pipes gets cool and the building gets warm, making use of the same type of components used in your fridge - a condenser, evaporator, and heat exchange unit.
Waste heat from the electrolysis unit and the fuel cell will be recovered to by the GSHP system, improving the efficiency even more.
The picture below shows the complete energy system for the Hydrogen Office:
The energy system will be connected to the national grid; however the energy system will export more electricity to the grid than it imports from the grid. The Hydrogen Office Ltd is a not-for-profit organisation, and any revenue resulting from electricity exported to the grid will be used to fund education, demonstration, research and development activities. The energy system, including the office's space and water heating will be designed to be self-sufficient for approximately 80% of the time.
In the future the project could generate sufficient hydrogen to power a car or minibus, demonstrating the potential to generate the energy to meet the transport needs arising from the building's activities.