Fair Isle

Fair Isle, UK Wind-diesel 100 kW All year round... 

Fair Isle is a relatively small island near the Shetland islands in the UK. The island s electrical and heat demand is provided by an existing autonomous power system comprising a diesel engine generating set and two wind turbines. Fair Isle is inhabited all year round and it is estimated that approximately 70 people live on the island. In more detail, the nominal capacity of the diesel generator is 35 kW, while the installed capacity of the wind turbines is 60 kW and 100 kW respectively (Glockner et al., 2004). 

Figure 5.5. Daily electric load profile of Fair Isle...

The analysis of both the existing wind-diesel autonomous power system and the proposed hydrogen-based power system of Fair Isle was conducted with the HOMER simulation tool. The detailed results of the analysis are presented in the following sections. 

Fair Isle Wind-diesel Power System... 

The configuration of the existing wind-diesel autonomous power system of Fair Isle is schematically presented in Figure 5.6. The main energy components of this system are a diesel engine generating set and two wind turbines. The identification of all kinds of costs for the main power components comprising Fair Isle s power system was also based on information derived from the RETScreen database (National Resources Canada, 1998). 

Similarly to the analysis of all other case studies, the objective of Fair Isle s autonomous power system simulation was the identification of all important operational parameters that will be used as a basis for comparison to the proposed hydrogen-based autonomous power system described in the next section. 

The analysis of Fair Isle s power system, which is currently in operation revealed that it produces 767,804 kWh per year, 92% of which is produced by the wind turbines. The analysis results related to electricity production and demand for the existing system of Fair Isle are summarised in Table 5.7. 

Moreover, the diesel generator operates frequently (3501 h/yr) in order to serve electric loads at periods of low wind resource and has an annual diesel fuel consumption of 24,407 L/yr. The monthly average electrical energy production of the existing wind-diesel system of Fair Isle is demonstrated in Figure 5.7. 

Therefore, we can conclude that there is a high potential for the introduction of hydrogen energy technologies in the system of Fair Isle in order to take advantage of the huge amount of excess electricity currently produced and dumped on the island. 

The economic analysis of Fair Isle s power system also showed interesting results. Despite the fact that the wind turbines capital costs comprise 82% of system s total capital cost, the annualised costs for the diesel generator constitute 51% of the total annualised cost for the existing wind-diesel system. This is attributed mainly to the high cost of diesel fuel and partly to relatively high diesel generator s annualised replacement costs. 

The total cost of energy produced by the autonomous power system of Fair Isle is estimated at 0.211 /kWh. All economic results for this system are shown in Table 5.8. 

It should be noted that the techno-economic analysis performed with HOMER software showed that the wind turbines installed on this island have been overdimensioned and this is the reason for the relatively high annualised cost attributed to wind energy for this system. On the other hand, this is a feature of Fair Isle s power system that most probably makes the introduction of hydrogen energy technologies economically viable. 

As noted before, in order to replace conventional power components with hydrogen technologies in renewable energy-based autonomous power systems, an oveidimensioning of RE equipment is usually necessary. Nevertheless, the results of Fair Isle s wind-hydrogen system optimisation revealed that there is no need for additional wind turbines on the island, due to the fact that in the existing wind-diesel power system the wind turbines were already oversized. More specifically, the first preliminary runs conducted with HOMER software demonstrated that the size of the wind turbines to be considered in the analysis will also be 100 kW and 60 kW, respectively. 

The analysis performed with HOMER showed that the optimal configuration for the wind-hydrogen power system of Fair Isle (schematically shown in Figure 5.8) comprises two wind turbines with a nominal capacity of 100 kW and 60 kW, respectively, a 35-kW PEM fuel cell, an electrolyser capable of producing 9 N m3/h H2 and a hydrogen storage tank with a storage capacity of 50 kg. 

Figure 5.8. Optimum configuration of Fair Isle s wind-hydrogen power system (NREL,...

Fair Isle Wind-hydrogen Power System Techno-economic Analysis As for all case studies presented in this chapter the scenarios for current and longterm costs for hydrogen energy equipment, presented in Table 5.5, were used in the techno-economic analysis of the optimum wind-hydrogen power system. 

As derived from the analysis presented in this table, the most significant total annualised cost factor comes from the fuel cell, which accounts for 48% of the total cost of Fair Isle s wind-hydrogen autonomous power, followed by wind turbines, which contribute approximately 36% of total annualised costs. Due to lack of seasonal storage for hydrogen in this system, the electrolyser and hydrogen storage tank are relatively small and therefore are considered as minor cost factors for this system. 

If we also take into account a potential increase in the cost of diesel fuel, which is more than just possible to happen in the future, it is evident that for the system of Fair Isle the introduction of hydrogen technologies will also have an economic benefit for the local community. 

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