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For remote communities and rural industry the standard is diesel generators. Remote electric power is estimated at over 11 GW, with 150,000 diesel gensets, ranging in size from 5 to 1,000 kW. In Canada, there are more than 800 diesel gensets, with a combined installed rating of over 500 MW. In the State of Chubut, Argentina, they have village systems using diesel generators, which range from 75 kW in a small village to 1,250 kW for a large village. Because the systems are subsidized, from the state to the national level, it is difficult to determine the actual cost of electricity. In general, past costs were $0.20 to $0.50/kWh; however, it is now quite a bit higher, as oil is over $100/bbl.

Diesel generators are inexpensive to install; however, they are expensive to operate and maintain, and major maintenance is needed from every 2,000 to 20,000 hours, depending on the size of the diesel genset. Most small village systems only have electricity in the evening.

In Canada there are more than 300 remote communities with diesel-generated electricity, and coastal Alaska has around 90 villages, which have the potential for displacing diesel fuel with wind (see Section 8.6 for wind-diesel performance at Kotzebue, Alaska). Australia, Argentina, northeast Brazil, Chile, China, Indonesia, Philippines, coastal sub-Sahara Africa, and of course other countries with isolated villages and islands have the potential for wind-diesel systems. The design of wind-diesel systems plus modeling techniques and simulation is better now that operational experience at a number of sites is available.

Wind-diesel systems were developed and tested at Riso National Laboratory, Denmark; Netherlands Energy Research Center, Petten, Netherlands; Atlantic Wind Test Site, Prince Edward Island, Canada; National Renewable Energy Laboratory, United States; United Kingdom; and at other locations. Primary work was on developing wind-diesel systems for the retrofit market. This market would be for existing diesel generators in windy locations, which would be over 50% of the installed capacity. A wind biodiesel system is being tested at USDA-ARS, Bushland, Texas [15].

Wind-diesel [16, 17] is considered because of the high costs for generating power in isolated systems, and by 1986, more than a megawatt of wind turbines were installed with existing diesel systems. Today, a very rough estimate indicates there are around 200 wind-diesel systems, but the market is changing rapidly with the high cost of diesel fuel. Two manufacturers expect to install over 1,200 MW of wind at existing diesel plants in 2008-2009. Simulation models for wind-diesel systems are available.

There are two aspects: addition of wind turbines to existing diesel power plants as a fuel saver, and now integrated wind-diesel or wind hybrid systems for village power. Wind-diesel power systems can vary from simple designs in which wind turbines are connected directly to the diesel grid (Figure 10.2), with a minimum of additional features, to more complex systems [18]. Wind-diesel power systems have peak demands of 100 kW to a megawatt, based on AC bus configurations, and storage is needed for high penetration. However, there are a number of problems in integrating a wind turbine to an existing diesel genset: voltage and frequency control, frequent stop-starts of the diesel, utilization of surplus energy, and the use and operation of a new technology. These problems vary by the amount of penetration (Table 10.5). Wind turbines at low penetration can be added to existing diesel power for large communities without many problems, as it is primarily a fuel saver. One solution for high wind penetration is the use of flywheels or battery storage [19, 20].

There have probably been more than 200 wind-diesel projects from prototypes to operating systems. Reports on operational experiences from eleven wind-diesel installations are available from the 2004 workshop [21]. The U.S. Air Force installed four 225 kW wind turbines connected to two 1,900 kW diesel generators (average load, 2.2-2.4 MW) for a low-penetration system on Ascension Island [22]. Average penetration was 14-24%. Tower height was limited to 30 m due to

load

FIGURE 10.2 (a) Low-penetration diesel without storage. Diesel governor and voltage controls maintain system power quality. (b) Medium penetration with system control and dump load for high winds and medium diesel power. (c) High penetration with flywheel storage.

load

FIGURE 10.2 (a) Low-penetration diesel without storage. Diesel governor and voltage controls maintain system power quality. (b) Medium penetration with system control and dump load for high winds and medium diesel power. (c) High penetration with flywheel storage.

available crane capacity on the island. Then in 2003, two large wind turbines (900 kW), controllable electric boilers, and a synchronous condenser were installed that brought the average penetration to 43-64% [23]. Fuel consumption was reduced significantly, with a savings of approximately $1 million per year. Wind penetration ratios exceeding 40% usually have stability problems; however, reliable and stable power was delivered at 80% power penetration. Cape Verde had eleven wind-diesel systems, with energy penetration of 14% and power penetration of 35%, with some problems [24]. Three of the systems were not working in 2005. Wales, Alaska, had a high-penetration

System control

AC wind turbines

Diesel gensets t

AC bus

Dispatched loads

Load

Fly wheel storage

Control dump loads

FIGURE 10.2 (Continued)

system (Figure 10.3) with battery storage [25, 26]. Wind turbines (3,250 kW) were added to the diesel system (four 1,200 kW) on King Island, between Tasmania and Australia, and wind power provided 18% of the electrical demand. In 2003, another 1,700 kW of wind power and a 200 kW battery and inverter system were added [27] to produce around 50% of the electrical demand. The large-flow vanadium redox battery reduces the variability of the wind energy.

Wind-diesel and wind hybrid systems are now available for village power, so the wind becomes an integral part of the original design [28]. A number of wind turbine manufacturers have wind-diesel or wind hybrid options [24]. These range from simple, no storage systems to complex, integrated systems with battery storage and dump loads.

Installation of wind-diesel systems and associated R&D has taken place for a number of years. There have been many configurations, but not too much consensus and replication. The technology is still not mature, and the village power market is not large enough. There is a lot of information from proceedings of wind-diesel workshops [21].

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Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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