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•       Overview:

Solar energy, as a new and clean energy, is a good resource to be used by people. More and more countries are starting to develop solar energy. We can see many applications of solar energy in our daily life, for example, solar energy water heaters and traffic lights. Our topic is about household applications of solar energy. We will talk about the development of solar energy, household solar-energy applications, and the advantages and disadvantages of applying solar energy.

 

• Definition (Introduction):

Fossil fuels, like coal, gas and oil, are produced by sunlight through photosynthesis over millions of years. Humans consume fossil fuels at a quite rapid speed. Moreover, using fossil fuels can also cause pollution. For example, vehicles need gasolines. Burning gasolines will release carbon dioxide which can aggravate greenhouse effect.

Although formation of fossil fuels depends on sunlight, solar energy comes directly from the sun. Solar energy is energy from the Sun’s radiation. People can get solar energy immediately rather than waiting millions of years. Moreover, the lifetime of the sun is quite long. As a result, there is no worry about running out of solar energy. Solar energy is a kind of clean energy. When people use solar energy, it will not produce wasted gases like cars do.

• Development (history):

Solar energy exists for a long period of time. It has been used by human for thousands of years. There are two main ways to use solar energy which are passive solar energy and active solar energy. Passive solar energy can be used as a heater. For example, allowing sunlight through windows to heat a place. Conversion of sunlight to electricity is the example of active solar energy.

In ancient, human mostly used passive solar energy. Ancient human used energy from the sun to keep warm by starting fires. They also designed buildings that can collect solar energy at daytime and release the energy to warm buildings at night. In other words, ancient people used solar energy as a thermal energy that can heat things. As time passes by, a French physicist named Edmond Becquerel discovered the photovoltaic activity in 1839. He found out that electrical current in some materials is increased when these materials are exposed to sunlight. In other words, Edmond Becquerel showed the conversion of sunlight to electricity. In 1905, the famous physicist Albert Einstein gave the principle of photovoltaics which is the photoelectric effect.

Based on understanding of photovoltaics and Albert Einstein’s photoelectric effect, human invented a solar cell in the mid 1950’s. AT&T Labs first developed silicon solar cells with 6% efficiency. The first practical application of photovoltaic cells is satellite systems. The Vanguard I, which was the first orbiting vehicle use solar energy, was launched in 1958. In 1960, Hoffman Electronics increased the efficiency to 14%. In the 1970’s, energy crisis made many countries aware of the importance of inventing renewable energy, like solar energy. In the same time, Dr. Elliot Berman of the Exxon Corporation decreased the cost of solar cells from 100 dollars to 20 dollars. It made many companies started to use applications of solar energy. Since the 2000’s, photovoltaic solar panels were affordable, and many photovoltaic solar panels were used in houses. Nowadays, researchers increase the efficiency of the solar cell to 20%. Compare with the first solar cell, today solar cells have much better efficiency.

 

• Application on Households

Solar energy can be utilized in different aspects of human life such as power plants, commercial use, ventilation system, swimming pools and solar cars and so on. We are going to focus on the application of solar energy in homes though. Population oversizing increases the pressure on conventional fuels. So the demand of alternative energy becomes larger and necessary. From Applications for Solar Energy, residential appliances can utilize electricity simply through solar power. Meanwhile, the solar energy can supply hot water by the running solar heater in homes. The main tool is the solar panel installed on the roof of the house, which capture and reserve solar energy on batteries.

The first step of considering the application of solar energy to household is to evaluate whether a home solar electric system work for your house, stated by U.S. Department of Energy. One should consider the following four criteria: the available solar resource for your home, the size of the roof to see whether it is able to install the solar cell, the economical consideration and the local permits and policies.

When solar energy is applied in practical use, what is the change? According to what Pia Ranada(2014) has observed on a Filipino family, they paid less and less for their power usage in a period of eight months because of installing solar panels. The family can get around 80% of their electricity from the sun. For a 3-bedroom house, normally the home’s roof is installed with 20 solar panels (as Figure 1 shown) that produce an average of 675 kwh or $185 of electricity monthly. Also in the article it is pointed out that often the family has more energy than they actually need. So in the past the family needs to pay around $555 to support the house daily appliances, now they make it get down to $277 or even less in the bright future.

Also, when utilizing solar energy, there is always possible that the solar panels will generate more energy than a household actually needs. But solar panels has an advantage of storing the excess energy which can be used later. For the last decade, solar energy as a new energy was difficult to utilize since the technology restrictions. As time passes, electricity which generated by the solar energy stabilizes more and can fulfill households daily demand.

• Relevant Project on Solar Energy

According to Energy Performance and Thermal Comfort of a High Efficiency House: RhOME for denCity, Winner of Solar Decathlon Europe 2014, we are going to introduce a solar energy-related competition called Solar Decathlon Europe 2014 competition which is held by LIFT (Interdisciplinary Laboratory of Technical Physics of Roma Tre University). The winning project designs a solar-powered building which is cost-effective, energy-effective and magnetic.

During the competition, 20 teams are required to operate a full-scale, innovative and sustainable house with usage of solar radiation. The projects are evaluated from the ten criteria: architecture; energy effective; comfort condition; communicating and social awareness; innovation; engineering and construction; electrical energy balance; house functioning; urban design, transportation and affordability; sustainability. We can see form these evaluations that the competition attaches importance to sustainability and recycling energy.

Figure 5 shows a cycle between the roof and the sliding system containing the pv panels, which allows the convective air movement to cool down the panels.

• Advantage & Disadvantage

Solar energy is widely applied to household nowadays because of its advantages. Most importantly, solar energy is renewable and environmental friendly, which means it will not produce pollution like fossil fuels. As a clean and renewable energy source, it does not release harmful gases like nitrogen oxide or carbon dioxide, which are the causes of global warming.

According to Solar Market Insight Report 2014, the result shows that the average American household generates 7.4 tons of carbon dioxide per year with the use of fossil fuels to produce electricity. By using the solar energy system, the environment is taking less risk to be damaged. Unlike fossil fuels, which have limited amount in the earth, solar energy is inexhaustible and can be used to produce electricity as long as the sunshine exists. Relied on the solar panels, people can utilize solar power at home to produce electricity and heat water. Although there is no sunshine at night, solar energy can be stored in the batteries and used later. It is obvious that the amount of fossil fuels need to be consumed will decrease with the increasing use of solar energy.

Using solar energy system is also an economic way for households. Compared with using fossil fuels, solar energy is much cheaper because people do not need to pay for the energy cost for producing electricity, and the cost of fossil fuels always occurs if people burn fuels. In other words, applying solar energy system can save a lot in the electricity bills for a household each year. According to the chart beside, the cost of solar is much lower than the kerosene. It provides direct evidence to prove that solar energy is economically feasible. Generally, solar cells do not need to pay much for the maintenance. They can be used for a long time after they are established. People only need to think about adding more panels for further use when previous ones are not enough, but do not need to worry about the problems that might occur in the panels because there is only a small probability.

Solar energy system is easy to be established in a house. Unlike wind and water power station, which require big devices to help run for electricity, solar panels can be easily installed on the rooftops and do not require any wires or cords. Because they are installed on the rooftops, they will not occupy extra place at home, which is very convenient. The application of solar energy is also good news for remote locations, where running power lines are costly and difficult. Solar energy can be used to produce electricity as long as sunshine exists, and it does not require the access to power cables.

Except for the various advantages, solar energy also has many drawbacks. Though solar energy is an economic energy during the process of producing electricity, it takes a lot at the initial installation. Even with the subsidy programs provided by government, individuals will not want to install solar system at home because of the high initial cost.

From the chart beside, we can conclude that module and installation fees are extremely high, compare with the cost for producing electricity. It might need to take more than 10 years to 15 years before you can break even with your initial investment. Adding up the initial costs, solar energy is quite expensive per watt compared with fossil fuels. For the poor countries, it is a big burden for them to afford the expensive initial cost, and they can only rely on the fossil fuels to meet their basic needs. With the development of technology, the initial cost of solar panels is decreasing, but it is still a little bit high. People would like to continue using fossil fuels, which is a familiar way in their life. However, it is worthwhile to reduce consumption of fossil fuels by using solar energy as a way to protect our environment.

Solar energy can work anywhere with the existence of sunshine, but there is a problem for the houses hiding behind the sunshine. Houses might be covered by trees or surrounded by high buildings, and they are not able to reach the sunshine during the entire year. As for the countries, like England, the weather there is cloudy at most time, and it is not possible for homes at that place to get power for generating enough electricity to meet the house needs. Also, during winters, sunlight is not strong enough like summer to provide sufficient power for the energy system.

As introduced above, solar energy is an environmental friendly energy compared with fossil fuels because it does not produce harmful gases, but most of photovoltaic panels are made up of silicon and other toxic metals. After the panels are broken or useless, the wreck will go back to the ground, and pollute the environment. What’s more, the quality and efficiency of solar panels can be effect by the environment pollution. For example, acid rain might corrode the surface of panels, and destroy its efficiency.

• Conclusion:

Solar energy does have lots of benefits. One of the most important benefits is that solar energy is environmental friendly energy. In other words, compare with fossil fuels, solar energy will not produce environment. Moreover, compare with fossil fuel, solar energy also can help people to save money, for instance, electricity produced by burning fossil fuel has higher cost than solar energy does. However, the using solar energy has higher initial cost than fossil fuel. For example, solar energy water heaters have much higher price than gas-burning water heaters. Moreover, solar energy cannot be used in every place. In some poor places, like Africa, they do not have the suitable environment for applying solar energy, not only because of lacking of knowledge, but also because of lack of standard condition for applying solar energy. If people can eliminate disadvantages of using solar energy in the future, which are high initial cost and environmental limitation, solar energy will bring more benefits to human and environment. In other words, if the solar energy can be widely used, it can benefit not only people’s daily lives, but also the whole environment.