DEMAND/SUPPLY MATCHING

4. MATCHING DEMAND/SUPPLY FOR SCOTLAND

Fig.9 Hydrogen production & utilisation over a year

Fig.10 Demand & supply during a winter week

Fig.11 Demand & supply during a spring week

Fig.12 Demand & supply during a spring week a summer week

The autonomous electrical load of a typical dwelling in Scotland needs to be supplied by 210 PV panels. This is because solar energy is not so regular and intense in Scotland and therefore a substantial amount of energy has to be stored as hydrogen during the summer months. Fig.9 shows the distribution of hydrogen stored (positive area) and then used to supply the deficit in demand via the fuel cell. A volume of 71.2 cubic meters of hydrogen must be stored during the summer to power the electric load during wintertime.

The system is not self-sufficient during the winter months. During January the required 430 kWh of demand cannot be feasibly met by the PV array therefore 17.5 cubic meters of hydrogen has to be supplied to the fuel cell. During spring there is sufficient power generated directly by the PV array to satisfy the electrical load. At this stage there is a balance reached and no net surplus energy is produced. The system is self-sufficient during summer and excess energy can be stored in the form of hydrogen for seasonal storage. In August, 13.2 cubic meters of hydrogen is stored to power the electrical load during the wintertime. The 210 PV panels required to power the dwelling have an area of 140 square meters and the fuel cell has a power rating of 2 kW to meet the electrical load of a typical Scottish dwelling.