How does Solar power Works Without the Sun?

1:01 AM How does Solar power Works Without the Sun? 1 Comment

1. • Alternative power sources such as solar and wind are being developed because they reduce pollution and green-house gas emissions while increasing the United State's energy independence. A major problem with solar energy is that it is only available when the sun is shining. Therefore, methods to transform and either store the energy until needed or combine it with energy from other sources have been developed.

   Thermal Energy:

   • One of the easiest ways to store solar energy is as heat. Buildings using passive solar heating are designed with large, south-facing windows and ceramic tile floors. During the day, the tiles absorb heat which is radiated during the night. Swimming pools are heated by pumping pool water through an array of solar collectors before being returned to the pool. During cloudy periods and night time, the water gradually cools. Using a cover when the pool is not in use greatly increases the retention of heat.

   Battery:

   • Solar energy can be converted by photovoltaic cells into direct current (dc) energy and stored in rechargeable batteries. When the sun is not available, the batteries provide electricity to devices such as lights, refrigerators, computers and televisions. If alternating current (ac) is needed, an inverter is added to the system. A solar power system with batteries is frequently used in remote areas where connecting to the electric power grid is not possible or cost prohibitive.

   Utility Grid:

   • Many owners of photovoltaic (PV) solar power systems are also connected to the utility grid. When the sun shines and their system is generating electricity, the solar generated electricity powers their household and any excess energy is sold back to the utility company. When the solar system is not generating electricity, the household buys electricity from the utility. At the end of the billing period, the credit for electricity sold is deducted from the cost of electricity bought. The federal government requires utilities to purchase excess electricity from homes and businesses using alternative energy generation. Some utility companies use large solar concentrator systems or photovoltaic power plants to generate power. Because the utility also has other sources of power, such as coal or hydro, the utility is able to balance the solar electricity generation with other sources to ensure a constant power supply.

   Future:

   • The U.S. Department of Energy (DOE) recognizes that increasing the use of solar energy requires new and better ways of storing the energy until it is needed. In 2008, DOE funded 15 new projects at a cost of $67.6 million to develop heat transfer and solar power storage.
     Several of these projects are researching ways to use latent heat transfer to store energy. When material is heated or cooled, it can change state. For example, water changes from a solid (ice) to a liquid (water) and then to a vapor (steam). In order to change state, heat is either absorbed or given off. This process of giving off or absorbing heat without changing temperature is known as latent heat transfer. When a solid becomes liquid, latent heat is absorbed. When the liquid becomes solid, the latent heat is released. Molten salt and other materials are being explored to find ones whose phase change can effectively store solar energy and release it when needed.