The world today requires energy for quite a number of things. Without energy the world will come to a standstill. For many years, the demand for power has been fulfilled through the use of fossil fuels such as natural gas, coal and products derived from oil.
Kulichenko and Jens claim that there was need to find new sources of energy after a while because of; high cost of traditional sources, difficulty of guaranteeing supply of traditional sources, global economic growth that has brought about a growing demand for more energy and increased global warming (52).
Solar power is inexhaustible, plentiful and clean energy. Solar technology is used to convert solar radiation to other forms of useful power. Solar thermal power plants are mainly located in extremely dry and uncultivated areas not used for agricultural activities.
Such areas provide the ideal or appropriate conditions for solar energy radiation absorption.
This report is about the Gemasolar energy plant located in Fuentes de Andalucía in Seville province of Spain. Gemasolar energy plant is a concentrated solar power plant which uses a central receiver technology with molten heat storage system.
The plant started working mid 2011.Technical feasibility of Central receiver technology was first proved during the 1980s by operation of six research power plants ranging from one to five MWe capacities and by one to ten MWe. A demonstration plant with a steam receiver was connected to the southern California grid.
The Spain Central tower receiver power plant was the pioneer commercial scale power plant globally that used this kind of technology. (Jayasimha 10) Without a doubt, solar power towers are to be the backbone of the entire power generation scheme.
The plant has the ability to take in sun rays and provide energy at night and also during cloudy days (Rirdan 102). Central receiver towers are large scale power plants.It is made up of two axis tracking mirrors or heliostats which reflect solar radiation at the very top of the tower where the receiver is placed.
The main goal of the Gemasolar project is to demonstrate the technical and economical viability of molten salt solar thermal power technologies to deliver clean cost competitive bulk electricity (Negewo 93). The plant is owned by Torresol energy investments.
Originally it was known as Solar Tres before the name was changed to Gemasolar. Torresol energy investment is owned 40% by Masdar, a company based in Abu Dhabi. 60% is owned by Sener from Spain (Hanna 45).
The Gemasolar power plant is made up of 185 hectares of solar field. The high tower receiver is 140 meters high. It also has 2,650 heliostats each having 120 square meters “distributed in concentric rings around the tower” (Negewo 92). Sodium and potassium nitrates make up the molten salt which is usually stored in tanks made of steel.
The biggest tank at the plant has a diameter of 23 meters and a height of 14 meters. The molten salt is used as heat transfer fluid and energy storage medium.
It is easy to manage the solar power due to the storage capacity of the steel tanks. It is supplied on demand. Connected to the tower at ground level are the hot and cold storage tanks. The tanks can store salts which provide energy for up to 15 hours without the sun.
Molten salts in the cold tanks are stored at 290°c and 565°c in the hot storage tank (“Cleantechchnica”:Spain Gemasolar). The implementation of the molten salt heat storage system allows creation and appearing of electricity when there is any solar radiation.
How It Works
Solar radiation first falls on mirrors known as heliostats. It is then reflected on to the receiver situated at the top of a supporting tower. Solar radiation is concentrated by the heliostats at 1000:1 ratio. This is controlled by a network of communication with 26 fiber optic rings present in it.
The orientation of the heliostats is automatically turned towards the sun by geared motors so that they reflect beam radiation on the receiver all day. A fluid flowing through the receiver absorbs the concentrated radiation and transports the heat to the ground level where it is used to operate a thermodynamic cycle.
“The receiver is capable of absorbing 95% of the radiation transmitted to the molten salts in the central receiver” (You tube: The World’s first Base load).
Cold salt is pumped up to the top of the tower at the central receiver where it is heated up. The liquid salt is brought back to the hot storage tanks being kept there at the temperature of 565°c. After leaving the storage tank, the heated salt is moved to the heat exchanger chamber via steam pipes and steam is formed as a result of condensation.
By means of this steam the turbines are turned; they generate electricity. According to Rirdan, any extra heat generated is kept in the molten storage tank and is used to produce electricity when the sun’s heat and radiation is absent.
Power generated is transferred to a substation located in Villanueva Del Rey, Andalucía, and further transmitted to the National grid system (102).
Cost of the project
Estimated cost of project was €171 million. It was financed by several financial institutions including European Investment Bank, Banco popular and Banesto ICO. Engineering, procurement and construction were done by Sense Company. This was inclusive of the development of a molten salt receiver and the manufacturing of heliostats.
A company called SGS was tasked with provision of assistance in the civil works for example construction progress audit, power limit substantiation, commissioning and initial operation of the power plant. Outukumpu was charged with the task of constructing hot and cold storage tanks.
The Nord block gear motors were manufactured by Nord drive systems. Working together, Schneider electronics and Hirscham electronics were the companies that built the communication network. It took 29 months to construct the power plant.
Energy output
Electric power is up to 19.9 MW. Net electric production expected per year is 110Ghw.The electricity generated of approximately 110 MWe per year is the highest electrical generation in the world for solar plants.
Advantages of the Gemasolar Technology
These are the reasons why the Central receiver tower technology is preferred to other renewable energy production methods. It has a prolonged operating time without solar radiation. This means that it can work through the night or on cloudy days using energy from the stored heated salt.
Energy output from this power plant is higher than that of other technologies in a facility with the same power. It has guaranteed electrical production for 6500 hours per year which is approximately two to three times higher than that of renewable energies. It is more scalable to any application both large and small thus it has significance to utilities.
It is more consistent energy supply with centralized and dispatch able generation model (Negewo 101). Its potential in MENA significantly exceeds any foreseeable regional demand even when quite onerous site conditions are required. It has significant potential for future development thereby reducing cost.
It works well with current large scale desalination technologies (Negewo 101).Other benefits of the central receiver power plant include: It provides clean and safe power to approximately 25,000 homes. There is less carbon dioxide emission by more than 30,000 tonnes a year (Enviromission Solar Tower 13).
In addition, the turbines do not have to be shut down quite often and hence the plant has a longer lifespan. The plants electrical generation can also be controlled to suit the demand for electricity.
Breaks or leakages are greatly reduced since there are no tubes or heat exchange fluids that spread out across the solar field and hence leads to low operational and maintenance costs (Rapier).
Conclusion
Solar is improving its cost and performance by 20 % each year and is expected to continue to do so for the foreseeable future (Seba 17).Concentrating solar thermal electricity is rapidly expanding in Spain and globally. In the USA, a first generation solar power thermal station of 354 MWe has been operating for more than 20 years.
As of mid 2011 about, 1100MWe of CST was installed globally. In principle, given sufficient land, 24 hours storage is feasible and solar thermal power can be operated either as base load, intermediate load or peak load depending on amount of storage installed and electricity prices.
Works Cited
Enviromission Solar Tower. Web.
Hanna, Nick. The Green Investing Handbook: .A Guide to Profiting from the Sustainability Revolution. London, UK. Harriman house limited, 2010. Print.
Jayasimha, Balakrishna. 2006. Application of Scheffler Reflectors for process industry: International Solar Cooker Conference, Granada, Spain. Web.
Kulichenko, Natalia, and Wirth Jens. Concentrating Solar Power in Developing Countries. Washington, DC., World Bank, 2012. Print.
Negewo, Bekele. Renewable Energy Desalination: An Emerging Solution to Close the Water Gap. New York. World Bank publications, 2012. Print.
Rapier, Robert. Power Plays: Energy Options in the Age of Peak Oil. New York. Apress, 2012. Print.
Rirdan, Daniel. The Blue Print: Averting Global Collapse.Louisville. Corinno Press, 2012. Print.
Seba, Tony. Solar Trillions: 7 Market and Investment Opportunities in the Emerging Clean-Energy Economies. Madrid. IMF Publications, 2010. Print.
Spain’s Gemasolar 24/7 Power Plant (VIDEO) 2011. Web.