Solar Photovoltaic Energy Systems

Solar voltaic cells based on crystalline silicon have operated with a 30% efficiency for experimental cells and 15-20% for commercial units available in 2008, at a cost of around 15 cents/kWh, compared to 4-7 cents/kWh for fossil fuel-fired power plants and 6-9 cents for those fired by biomass. Costs of photovoltaic electricity have shown a continuous downward trend. Part of the high cost in the past has resulted from the fact that the silicon used in the cells must be cut as small wafers from silicon crystals for mounting on the cell surfaces. Significant advances in costs and technology are being made with thin-fllm photovoltaics, which use an amorphous silicon alloy. These cells are only about half as efficient as those made with crystalline silicon, but cost only about 25% as much. A newer approach to the design and construction of amorphous silicon film photovoltaic devices 

FIGURE 17.19 High-efficiency thin-film solar photovoltaic cell using amorphous silicon. 

---

Solar energy systems are solar home systems, solar photovoltaic (SPV) systems, solar water heating (SWH) systems, solar dryers, and solar cookers. These systems are installed and managed by a household or a small commirrrity. A solar home system is a PV system with a maximum capacity of 40 W. 

The world net electricity generation has been estimated to increase 77% from 18 trillion kilowatt hours (kWh) in 2006 to 31.8 trillion kWh in 2030 with a value of 23.2 trillion kWh in 2015 >. On the other hand, the world market capacity of solar photovoltaic power systems escalated from 1.3 gigawatts (GW) in 2001 to 15.2 GW in 2008 for systems which have been installed. In particular, market installations reached a record high of 5.95 GW in 2008 corresponding to a growth of 110% from 2007. The contribuhon of solar energy to the world net electricity generation is estimated to be 6% by 2050. 

Krauter, Stefan C. W., Solar Electric Power Generation—Photovoltaic Energy Systems, Springer, New York, 2006. 

A. Marti, G.L. Araujo, Limiting efficien-des for photovoltaic energy conversion in multigap systems, Sol. Energy Mater. Solar Cells 43 (1996) 203-222. 

NFPA 70 National Fire Protection Association 70 is also known as the National Electric Code (NEC). Revisions and addendum s to the code are currently being developed that specifically address fuel cells. Article 690 - Solar Photovoltaic Systems has been targeted for revision to include fuel cells and alternate energy sources systems. This proposal is not expected to be approved since the technological and operational differences between fuel cells and photovoltaic systems is considerable. A new article, currently identified and Article 691, has been proposed and applies to fuel cells for buildings or residential dwellings. This standard addresses the electrical interface between the fuel cell system and a building s electrical distribution panel. 

Bilgen E (2001) Solar hydrogen from photovoltaic-electrolyzer systems. Energy Conversion and Management 42 1047-1057... 

A solar photovoltaic system contains, in addition to solar cells and module(s), an array structure to support the modules, power-conditioning circuitry for control and modification of the output, and a means of storing energy if required. All elements beyond the module are referred to as balance-of-system (BOS) components. The cost of BOS items is nominally about equal to the cost of the PV module. However, the BOS fractional cost contribution can vary from one- to two-thirds of the total installed cost of a system, depending on application. 

---