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Stand-Alone Power Supply (SPS) System Module 1Why Do We Need Energy? | The Fossil Fuels | Why the Need for New Sources? | Energy Supply in WA | Renewable Energy Resources | Why Stand-alone Power Supply (SPS) Systems? |Why Do We Need Energy?It is an essential service.
The Sun drives the natural environment - Fossil fuels drive the economy...Energy is an essential service. This means that we cannot live in a technological world with out it. Other essential services include food, water, shelter and heating. This is especially the case if you have lived with energy services, such as grid provided electricity and move to remote locations where you need to provide your own electricity, as the grid is most often available in areas with many people. The Sun provides all the energy that is used in the natural world, for example plants use sunlight and carbon dioxide to produce oxygen and carbohydrates, which as humans we (and many other organisms) need to survive. The economy is driven by the availability and use of fossil based fuels such as coal, oil and natural gas. These fuels are the decomposed remains of ancient animal and plant life.
The Fossil FuelsFossil fuels are energy sources which come from fossilised plant and animal material.
There are a range of fossil fuels, but most are derived from the three basic resources of:
Transport fuels such as petrol, diesel, etc are produced from crude oil which has been refined. Why the Need for New Sources?Fossil fuels are a non renewable resource. There are limited reserves of most of the fossil fuels. The following list is a generalised estimate of how long each is expected to be widely available at an acceptable economic costs:
Concern for the environment and increased economic cost is likely to result in the reduced use of fossil fuels before the supply runs out. Fossil fuels come from ancient animal and plant material which has decomposed very slowly in a limited oxygen atmosphere. This process is exceedingly slow, in the order of hundreds of thousands to millions of years. For this reason, fossil fuels are considered a non renewable resource. As the rate of demand for these materials is much greater than their predicted lifetimes, and increasing, we only have limited reserves of these available. According to our best estimates, we have approximately 40 years of oil left, about 80 years of natural gas and 200 years of coal reserves. However, concerns about the environmental effects of mining these resources and the inherent impacts and dangers of some forms of mining, their effect on the air quality (particularly in urban areas), and Global Warming may lead to restrictions on the use of fossil fuels within 1 – 2 generations. Energy Supply in WAThere are typically 3 sources of publicly available energy supplies in Western Australia Utility provided electricity - Western Power Corporation (Retail)Domestic tariff 13.94 c / unit. (Non-utility generated electricity cost are much more variable, but much greater than 14c / unit.)
Reticulated Natural Gas - Alinta (Metro, Albany, Kalgoorlie, Geraldton)4.55 - 7.01 c / unit Bottled Gas (LPG)30 c / unit (variable) 
Figure 1 Different types of power stations in Western Australia and the two independent electricity grids in green and yellow.
Renewable Energy ResourcesRenewable energy resources, such as solar and wind are variable. The average amount of energy available changes monthly and may also depend on the site. Some commonly used renewable energy resources are;
One of the down sides of renewable energy resources, particularly solar and wind is that they are variable sources. There are periods of time when the sun doesn’t shine or when the wind doesn’t blow. There is also variability associated with the amount of energy available seasonally. This variability is taken into account by system designers when designing your Stand-alone Power Supply (SPS) system. The Average Solar Radiation ResourceFrom your own experiences, you will already know that there is much less sunlight available in winter than summer, in part because of the increased cloud in winter but also because of the way they Earth orbits the around the sun in conjunction with the Earths tilt.. 
Figure 2 The solar resource throughout the year in Australia.
Three ranges of data can be used to quantify the solar resource at a particular location:
Systems, which are designed with less accurate design methods (i.e. no data) usually, have larger panels to allow for variability in the solar resource and site conditions. When designing your SPS system, designers take into account how much energy is available on a typical day. To do this, meteorological information is used. There are three ranges of data; no data, monthly averaged data and averaged hourly data. Systems can be designed when there is no specific data about a site using generalised solar resource maps, such as this one produced by the Australian and NZ Solar Energy Society. However, this data is less accurate than when specific data is available from organisations such as the Bureau of Meteorology or from site monitoring. As a result, systems are designed with a larger number of panels to allow for the uncertainty in the data. 
Figure 3 The Western Australian Solar Resource.
The Wind ResourceThe greatest challenge to the economic use of wind power is its variability. Monitoring of site with anemometers is used to determine monthly average wind speed. Sometimes, data for nearby location already exists which can be used. As with solar data, wind data is required for SPS systems which will incorporate a wind turbine. As the economic effectiveness of the system is very reliant on the quality of the wind resource, monitoring of potential sites must be undertaken. General resource maps are good for identifying places you wouldn’t consider for a wind system, but do not provide enough information to allow system sizing to be undertaken. 
Figure 4 The Western Australian Wind Resource at a height of 30m above the ground.
Why Stand-alone Power Supply (SPS) Systems?In large parts of WA where there is no electricity supply, thus there is a need to supply your own power. These systems are commonly known as Stand-alone Power Supply (SPS) systems, as well as Remote Area Power Supply (RAPS) Systems. Western Australia is one of the largest states in the world. It is larger than many European and Asian countries. Most of the state also has a low population density (few people per square kilometre). For this reason, it is very difficult and expensive to provide a statewide grid. Two main grid areas exist, the South West Interconnected System which is shown in green in Figure 3 from Western Power and the Northwest Interconnected System (yellow). Most larger towns in WA also have their own smaller distribution systems which are either owned by Western Power or a private electricity provider. In locations outside of towns, or where there is no distributed electricity, people need to produce their own power for their homes and businesses. This is the end of Module 1. |
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