Solar energy is readily available and the source of energy is not expected to expire as is the case with traditional fossil fuels (actually fossil fuels are just altered form of solar energy). It has the most brightly future among various renewable energy. However, despite the rapid growth in recent years, solar power accounts for less than 1 percent of electricity use in the United States. To take place of fossil fuels in the future, it still has a long way to go. In my opinion, innovations should be happened in more directions, not just the PV, to make the technology more efficient. And reduce the cost to make more people switch to it in the future.
PV technology is truly developing rapidly these years after the National Center for Photovoltaics chartered in 1996. 40% efficiency barrier broke in 2006 and terrestrial PV shipments exceeds 10 GW in 2009. The worldwide PV production grew by lager than 100% in 2010 with the pirce decreased at the same time . However, PV is just a part of using solar energy. How to store solar energy for use at night or on cloudy days? The storage problem is also important in solar energy. Sensitive heat storage technology has reached commercial level, but still limited to its low storage density and large volume of storage unit. Chemical reaction storage technology needs certain safty requirments and large investment, still remain in small-scale experimental level. Recently, some researchers from Northwestern University have developed a carbon-based material that could revolutionize the way solar power is harvested. Due to Earth’s abundance of carbon, carbon nanotubes have the potential to boost the long-term viability of solar power by providing a cost-efficient option as demand for the technology increases. In addition, the material’s mechanical flexibility could allow solar cells to be integrated into fabrics and clothing, enabling portable energy supplies that could impact everything from personal electronics to military operations . Therefore, such innovations should be highly encouraged. Even if we solve the storage problem in the future, energy transportation problem comes out. As we koow, because of the geographical locations, different areas have different capabilities to caputre sunlight, but we should ensure that global populations have easy access to constant and reliable solar energy. So how to transport stored sun power from low supply area to high demand area become important.
Another key problem in solar energy development is the huge investment and cost, which lead to less than 1 percent of electricity use in the US. To solve this problem, government subsidy will be as important as technology breakthrough. China is example which government subsidies played a significant role in solar energy development. Loans at very low rates from state-owned banks in Beijing, cheap or free land from local and provincial governments across China, huge economies of scale and other cost advantages have transformed China from a minor player in the solar power industry into the main producer of an increasingly competitive source of electricity . But China’s commitment to renewable energy is expensive. Although costs are falling steeply through mass production, solar power is still at least twice as expensive as coal. Then the government charges a renewable energy fee to all electricity users. The fee revenue goes to companies that operate the electricity grid, to make up the cost difference between renewable energy and coal-fired power.
And sometimes we may come back to the most traditional way to use solar energy. Almost every country around the world chooses to dry the clothes by airing except the US. People in the US prefer to use the dryer because airing the clothes is illegal in most states. However, a report shows that about 6% to 10% of the electricity is used on dryer for a normal family in the US . It could be a huge reduction of fossil fuel consumption if most states follow the step of Utah and Florida, they unlimited the rights of airing clothes outside in 1999.
Since the solar energy is the most likely renewable energy which can replace fossil fuels in the future, these problems must be solved before fossil fuels run out. Just as Dr.Steven Chu, the Energy Secretary said, “We need some innovations in solar energy ”.
 Photovoltaics (Solar Cells), April, 7, 2006
 Sciencedaily, Sep 27, 2011
 New York Times, Sep 14, 2011
 Energy Star Market & Industry Scoping Report, Nov, 2011