Solar energy: perpetual low-cost power generation

By Chaudhry Kamran Naseer

The use of solar energy for human perquisites is not something new. It has been used for decades by a number of countries due to the various benefits it provides to people, most notably for power production. Thus, its demand has been increasing day by day because of concerns about the lack of availability of fossil fuels for producing power in near future, which has led to rise in petroleum products and the global climatic change that is taking place owing to carbon emissions from fossil fuels.

In this context, the main problem associated with the use of solar energy for power production at commercial level is high capital cost. However, technological advancements in this field have solved this problem. Today, such techniques have been discovered which integrate the advantages of solar energy with those of fossil fuel power technologies for clean, low cost and efficient energy production, thereby cutting the installation costs of solar equipments.

Regardless of the type, in each power plant, heat production is the primary focus for which different types of fuels like coal, oil and gas are used. The heat generated is then utilised to rotate the turbine necessary for electric production. For a high capacity power plant, more heat will be required. Using concentrating solar thermal power (CSP) technologies like solar trough technology, Fresnel lens technology and power tower technology etc, an additional source of heat is provided to fossil fuel power plants. These CSP technologies concentrate on sun light and then use it to produce heat.

As CSP technologies only add heat in the power cycle, while converting a fossil fuel power plant into integrated solar power plant will not require comprehensive alteration and addition of new machinery. However, existing equipments such as steam generator, turbine, condensing system etc., are used which reduce the installation cost of a solar system not possible in an ordinary pure solar power plant.

Further as only sun light is used for heat production, its running cost is zero which reduces fossil fuel consumption significantly, consequently, lowering electricity costs and carbon emissions.

Hence, solar energy is combined with fossil fuels to produce electricity reducing fuel consumption, electric cost and carbon emissions. New integrated solar power plants are neither totally fossil fuel fired nor renewable but a mixture of both.

Using CSP technologies, steam of different temperatures like 550 degree centigrade in power tower technology and 270 degree centigrade in fresnel lens technology can be obtained. This makes it possible to convert a specific type of thermal power plant (steam turbine or combined cycle) into integrated solar power plant, as each plant has its own steam temperature value.

When fossil fuels are used for power production, a certain amount of carbon dioxide is emitted which is not only hazardous to one’s health but is also a major source of risk for the global environment as it destroys the ozone layer. Emissions of carbon dioxide from coal and gas are 1,900 lb / MWh (pound per mega watt hour) and 1,200 lb / MWh, far more as compared to solar energy (2 lb / MWh only). Using solar energy as part of power generation reduces the overall carbon emissions significantly.

Generally the share of solar energy in integrated solar power plants is between 20-75 mega watts. This quite clearly proves that a significant value of carbon dioxide emissions can be reduced by using solar energy in power plants.

Likewise, a huge mass of fuel can also be saved. By using the formula and calculating the energy density (heating value) of coal, we find out that coal power plants obtain approximately 2MWh electricity after burning 1,000 kg coal. Hence by generating 20-75 MWh electricity from the Sun, in an integrated power plant, approximately 87.6-328.5 million Kg coal can be saved per year. This enormous reduction in fuel consumption will also cut the cost of electricity produced.

Furthermore, in summer when the electricity load increases due to great usage of cooling equipments which require more power, solar energy will be ideal for such a condition. This is because during each day’s peak hours, maximum heat from the sun light can be captured and in this way, improve the efficiency of the power plant.

Although CSP technologies can be used for both types of thermal power plants (steam turbine or combined cycle), but due to high efficiency of combined cycle as compared to steam turbine, most of the thermal power plants that are being installed are combined cycle. So these technologies are generally being utilised in combined cycle power plants which after integration are called Integrated Solar Combined Cycle (ISCC) power plants.

As a result of these advantages, integrated solar combined cycle power plants are being installed in different countries. The details of some of these plants are provided in the table.

ISCC projects in countries like Egypt, Mexico, and Morocco have been approved by the World Bank. The ISCC plant in Morocco is expected to start operating in April 2010. ISCC plants in some other countries like Iran have also been proposed.

While discussing Pakistan, 65 per cent of electricity is produced from thermal resources. Reduction of this high dependency on thermal power plants is needed, as these power plants utilise scarce gas and oil reserves and disturb the BOP balance by increasing petroleum imports. Not just this, there is also costly electric generation and high carbon emissions which take place. Furthermore, our country is currently facing a big crisis in the energy sector and due to the gap between demand and supply of energy; many sectors of the economy have been affected.

To reduce the energy crisis on a permanent basis which is necessary for high sustained economic growth, Pakistan needs a long term, comprehensive energy policy. This should be especially focused on low cost energy production, which is only possible if cheap energy resources available in the country are utilised optimally.

Pakistan’s climate is suitable for solar power production as it is one of the few countries in the world where the availability of Sun’s heat is up to 16 hours on average. With respect to the coal, Pakistan is the fifth largest country of the world having an abundant quantity of coal reserves.

If thermal power plants in Pakistan are converted into integrated solar power plants, a large quantity of fuel can be saved which would reduce the production cost of electricity, preserve fuel reserves and protect the environment from carbon dioxide.

Hillary Clinton has announced that the US will help Pakistan in dealing with the energy crisis. Pakistan must get assistance from developed nations to not only install new integrated combined cycle solar power plants but convert the existing thermal plants into integrated solar power plants. Beside this, specific attention is required to improve the skills of labour to be able to perform efficiently in a technologically advanced environment and for this, it is utmost important to educate the labour.

Under construction integrated

solar combined cycle power plants

Country          Total power  Solar contribution

Egypt  140 MWe   20 MWe

Morocco          472 MWe   20 MWe

Algeria 130 MWe   25 MWe

Florida 480 MWe   75 MWe

Source: wikipedia.org

http://jang.com.pk/thenews/dec2009-weekly/busrev-14-12-2009/p10.htm