Keywords: renewable energy region, 100% renewable energy self sufficiency region, Pellworm Island, renewable energy in Pellworm Island.
Pellworm is one of the North Frisian Islands located in the North Sea coast of Germany (Figure 1). It is a part of the Nordfriesland district in the Federal State of Schleswig-Holstein. Its area is 37 km2 and the population is around 1,200 inhabitants. Together with some smaller islands, Pellworm forms “the Amt Pellworm”.
Background of Renewable Energy Development
Pellworm Island has pioneered the utilization of renewable energy since early 80’s. After that period, the development is increasing. The island economy is based on farming and tourism, with an overwhelming predominance of the service sector. Due to the acute seasonality of the tourist industry, its energy needs are one of the major conditioning factors of the energy self-sufficiency project. Another essential aspect that defines the case of Pellworm is the fact that the island is connected to the mainland electricity grid in Germany via submarine cables. The idea was to break this connection in the immediate future and create a self-sufficient, 100% RES system.
Renewable Energy Plan
In 1997, a renewable energy plan for Pellworm was drawn up. The title was “Energy Supply on the Basis of Renewable Energy Sources Using the Example of the North Sea Island Pellworm – A Local Development Plan”. The goal of the development plan was to present model concepts for energy supply based on renewable energies and to access a broad spectrum of applications. Special emphasis was given to wind power and biomass and to ways of storing energy. Pellworm’s strategy for the future is based on fully exploiting its main sources of renewables: wind, sun and biomass.
Wind power has the greatest potential of the island’s renewable energy. In the late 70’s, experiments were started with wind generators. There were 16 wind generators (2001). These generators represented an installed power of 5.9 MW. The output was 15,100 MWh/year. Potential of wind power in the island was estimated around 91,500 MWh. It leaved a wide enough margin for the project of wind power in the future. The study indicated that the longest periods of recorded calm (with no wind) did not exceed 74 hours.
Basic biomass resources are focused on harnessing energy from straw and manure to offer energy complement to cover the eventually of variable winds. The inventory of available biomass even includes harnessing grass cutting from the edges of the roads. The renewable energy plan calculated that biomass potential in the island was around 7000 MWh/year. This biomass potential could be used to produce moderate heat and to supply electricity. The proposal of renewable energy plan was based on power station with capacity to produce around 1 MW of heat and 200 kW of electricity.
There were nearly 8,000 m2 of photovoltaic installed (2001). In 1983, the first plan of 300 kW was installed. This plant stopped to operate in 1989 and was undergoing re-organisation. In 1992, the new photovoltaic plant was installed. The plant had the same power and resulted a production of 225 MWh/year.
Heat Pumps and the Increase in Energy Efficiency
One aim of the plan was to bring heat pumps to be used in at least 500 of 674 residential buildings of Pellworm which consumed around 13,000 MWh/year of heat. By utilizing heat pumps, electricity requirements could be cut into around 4,300 MWh/year. It was an essential step in the design of energy self-sufficient model.
Advances of the studies done for Pellworm suggested that almost half of the hot water requirements could be met by solar thermal energy. Those study results increased the number of solar installation. There were 28 solar installation with a total area of 318 m2 (2001). By producing hot water in this way, there would be an approximate energy saving of 127 MWh/year. The plan intended to install solar thermal energy in 270 buildings (40%) of the total buildings (674 buildings) in the island, which would provide 390 MWh/year of heat.
Available liquid manure (slurries) was around 11,000 m3/year. This number was based on the possibility of concentrating the effluents of 70% of the livestock holdings. Cost analysis suggested that the generation of biogas would only be feasible with a centralized system using methane digester. Within the context of 100% RES for Pellworm, two biogas production have been analyzed (46 kWel and 200 kWel). The smaller version gave better continuous performance. The larger version would provide greater storage power with sufficient capacity to cover windless days.
Total energy resulted from renewable energy is around 22.5 million kWh/year. That is about twice of the island’s power need. The energy is used not only for recreation but also for power supply. The excess energy is supplied to the mainland through the grid.
Electricity from Solar Energy
As a region which is rich with the sun light, energy resulted from solar per year is around 1,000 kWh/m2. In the reason of solar cell efficiency about 16%, energy resulted from solar is around 160 kWh/m2. The whole island obtains energy from solar totally around 2.2 million kWh/year. It is equal to 220,000 liters of oil.
Electricity from Wind Energy
There are 12 wind turbines currently in the Pellworm Island. These wind turbines produce in total 15.85 million kWh electricity or equivalent with 1.585 million liters of oil. Only a few wind power generators were erected in the north-east and are not likely to extend beyond the actual confines, due to restrictions by regional planning. However, one of the largest hybrid renewable energy plants in Europe is located in Pellworm (Figure 2). It combines photovoltaic and wind energy to provide over 700 MWh/year electricity. This largest hybrid plants has been operated by E.ON Hanse AG.
Electricity and Heat from Biomass
Fermentation of cattle and pig manure and plants produce methane (CH4) created by internal combustion engine. A generator convert this biomass into electricity. Pellworm Island obtains 4.2 million kWh/year of energy from biomass, only 30% of this energy can be converted into electricity. The waste heat is used for heating in the resort.