Solar energy is a clean, safe and sustainable source of energy that has become increasingly popular in the 21st century. There are various technologies available to harness solar energy, including solar panels, which are made up of photovoltaic cells that convert sunlight into electricity. While there are still technological challenges to overcome, there have been promising developments in the field. The future of solar energy lies in the construction of new buildings and retrofitting older ones with solar panels. Large solar-powered electricity generating stations are also being developed, but require a significant amount of space. Other possibilities for the large-scale exploitation of solar energy include concentrated solar technology and power towers. The future of solar energy depends on the support of governments and citizens around the world.
In the 21st century, solar energy has already become part of everyday life. From solar heated swimming pools to solar powered homes, there are many examples demonstrating the beneficial application of clean, safe and sustainable energy from the sun. As concern grows about the effects of burning fossil fuels and the possibility of depleting non-renewable energy sources, the future of solar energy looks bright. As of 2013, the technology is not without its problems and so far the applications have mostly been on a relatively small scale, but there is a lot of research going on in this area and there have been a number of very promising developments.
Harness solar energy
The sun is potentially a huge source of clean, renewable energy. Some estimate that sunlight could produce 10,000 times more energy than Earth used in the early 21st century. There are, however, major technological challenges to effectively harness this energy. There are several technologies available and under development that use sunlight to provide energy.
Sunlight can be used simply to heat water which is then used for central heating of homes. Alternatively, it can be used to generate electricity using photovoltaic (PV) cells arranged on solar panels. A third method is to focus sunlight on a target to generate heat, which can be used directly for industrial purposes or to provide electricity.
Solar panels
These panels are based on the photoelectric effect, where certain substances produce a small electric current when exposed to light. Photovoltaic cells are built to take advantage of this effect, and solar panels are made up of large arrays of these devices positioned to receive as much sunlight as possible. Together, they can generate significant amounts of electricity. While, as of 2013, they are relatively inefficient, they normally have very low operating and maintenance costs and can be very effective at providing energy to homes. There is a lot of research going on to improve efficiency and build cells with cheaper materials.
Most solar panels are made up of crystalline silicon photovoltaic cells, which are 14-16% efficient at converting sunlight into electricity. However, several alternatives are being studied. Thin-film cells can be made from a variety of materials. While these are currently less efficient than standard PV cells, they are lightweight, flexible and cheap to produce. Multi-junction cells can achieve an efficiency of over 43%. They are structured so that different parts of the cell are tuned to capture sunlight at specific wavelength ranges, rather than having a single receptor lose some of the available energy.
Another promising area is the dye-sensitized solar cell (DSSC), sometimes called the Gratzel cell, after Michael Gratzel, who first developed it in the 1990s. These use a dye to capture solar energy and produce a flow of electrons, which are replenished via a layer of liquid electrolyte underneath. While potentially cheap to produce, they are only about 12% efficient, and there are durability issues that can affect commercial use. For example, liquid can freeze in cold conditions or expand when hot and could leak. Researchers have developed a version of the cell in which the troublesome liquid electrolyte is replaced with a solid material, paving the way for cheap and durable solar panels.
In addition to the development of cheaper and more efficient photovoltaic cells, an important part of the future of solar energy lies in the construction of new buildings and the retrofitting of many older ones. Some experts predict that most, if not all, new buildings will have solar panels installed on their roofs. Since these are also easily installed, many older buildings can receive upgrades to run on solar energy. Experts and environmentalists hope that building green energy will be encouraged by governments through generous tax incentives, exemptions and subsidies for the use of alternative energy.
Solar panels on a roof can, in some areas, supply all or most of a home’s energy needs. Where people live in multi-story dwellings, however, the amount of roof space is very small compared to the number of dwellings. While small, individual applications can relieve some of the strain on the electrical grid, if the sun is to meet the energy needs of cities and industries, its future must lie in large solar-powered electricity generating stations.
The biggest problem facing the exploitation of solar energy using photovoltaic cells is the space required to build power plants. A system is made up of thousands of solar panels, not unlike those currently installed on alternative energy homes. For this reason they require a consistently sunny area and a significant amount of space. Currently, one of the largest power plants in the world covers more than 10 square miles (16.9 km2) and creates enough electricity to power approximately 200,000 homes. Some experts suggest that an area about 100 miles (160.9 km) on each side would be required to supply the entire United States with power, probably somewhere in the desert climate of the American Southwest.
Alternatives to solar panels
There are many other possibilities for the large-scale exploitation of solar energy. One example is concentrated solar technology (CSP). Instead of generating electricity directly, they concentrate sunlight to heat water, providing steam to drive a turbine that produces electricity just like a conventional power plant. They can consist of arrays of parabolic mirrors that focus sunlight onto a liquid-filled linear tube. Alternatively, the sun’s heat can be focused by a parabolic mirror to heat a fluid that drives a Stirling engine, which supplies the mechanical energy for electricity generation.
Another proven system is the “power tower,” in which an array of solar-tracking flat mirrors focus the sun’s heat onto a container of liquid that’s used to supply steam to a generator. A few plants are in operation producing 10-20 megawatts of electricity. Future plants could deliver up to 200 megawatts.
The future
An encouraging trend regarding the future of solar energy is that many of the world’s biggest innovators are choosing to focus their talents and funds on improving alternative energy technology. Many award programs, funded by various governments around the world, focus on providing solar energy economically and at scale. In many countries, citizens receive financial incentives for switching to green energy sources and installing their own solar panels.
While there are many encouraging signs as of 2013 that governments are recognizing the need for alternative energy sources and promoting solar energy research, the answer lies partly in the hands of the citizens of the world. What ordinary citizens choose to buy and support will influence future trends. By installing solar panels, donating to research organizations involved in alternative energy, earning a degree in a related subject, and voting for measures that promote the development of alternative energy, anyone can have a say in the future of solar energy.
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