Solar Photovoltaic Panels
Sunlight is directly converted into electricity through usage of these silicon based systems equipped with solar panels and no moving parts. Direct current or DC electricity is produced by such systems similar to batteries. Consequently, DC is transformed into AC or alternating current through inverters powering various household appliances. A key benefit of inverters is that they allow connection of systems to electric utility distribution grids. This essentially means that power can be sold to the utility when not used onsite. These grid-connected photovoltaics are the simplest and most common PV systems installed on houses. PV systems may also be connected to batteries allowing for electric storage.
Types of Applications
- Off-Grid PV systems for remote applications
Off grid PV or photovoltaic systems are an excellent source of independent electricity derived directly from the sun. These are not tied to electrical company grid systems. As a result, when surplus electricity is produced greater than demand, these systems can be applied towards charging of batteries for storage. Off-grid systems are perfectly suited for remote locations where electricity demand is typically low or there is no power grid to connect to. These systems also allow customers to be independent of electrical companies.
Off grid systems have multiple applications especially when there is power loss or a black-out. With them in place, we continue to have electricity at our disposal to run furnaces, sumps, well pumps or air conditioners. These systems are particularly useful in remote areas where there is no grid to supply power. Further, the solar panels can be fitted to provide shade or avoid direct sunlight striking roof tops thus bringing down the temperature and ably cooling dwellings. Additional applications include livestock electric fences, aerator pumps in low oxygen ponds
Typical components of an off grid system are solar panels, wiring, inverters, backup generators, batteries, system meters, charger controllers, rectifier, main DC disconnect and AC breaker panels. Panels mounted on roofs or rack systems facilitate transformation of sunlight into current through photovoltaic cells. The inverter converts DC to AC. The generator is an integral element of off-grid systems and is used in periods of low sunlight. Typically, its usage is when used is when batteries are low. The main purpose of batteries is to store energy not used during low consumption periods. System monitors display battery charge, system performance and panel output. The main DC disconnect is meant to be a fail-safe mechanism when using batteries and to avoid electric shock during maintenance of batteries. Charge controllers ensure that batteries are optimally charges and are intended to prevent over-charging.. Rectifiers are used to re-convert remaining AC into DC to re-charge batteries with production of extra current. Breaker panels are one of the key elements where all home circuits begin and terminate.
- Grid-Tied PV systems for household applications
Apart from off-grid PV systems, there are also grid-tied PV systems available in the market for primarily household applications. True to its name-sake, a grid-tied PV system is essentially connected to the grid and supplies power into it. These grids are usually independent and large grids such as public electricity grid. Grid-tied systems come in various sizes from household (2-10kWp) to solar power stations (up to 10s of GWp). The purpose of grid-tied PV systems is to generate decentralized electricity.
For residential PV systems tied to the grid, the demand for electricity is supplied by the PV system itself. Any excess that is generated is fed back into the grid. The grid absorbs the excess electricity by transforming Direct Current (DC) into Alternate Current (AC) through the usage of a special grid-controlled inverter. These grid connected inverters are designed to supply electricity (AC) in sinusoidal form i.e., synchronized as per grid frequency. They also ensure that the voltage fed into the grid does not exceed the grid voltage and allow household PV systems to disconnect from the grid in case the grid voltage is off.
Feed-in Tariffs and Net Metering
Net metering refers to the “net” of “what remains after deductions” i.e., the difference between energy outflows and metered energy inflows. The concept pertains to the renewable energy facilities such as solar power. Under this system of net metering, grid-tied PV system owners receive credit for the electricity they generate into the grid. The electricity meters used for this purpose are designed to record in both directions so that PV system owners can bank the excess electricity generated by their systems into the grid for future credit.
On the other hand, a Feed-in Tariff also known as FiT, refers to the premium price paid to eligible households and businesses for the renewable electricity generated by them into the grid. This guarantees that renewable energy investors get reasonable returns on their investments into energy. Unlike Net Metering which is more of an accounting procedure, FiT ensures that grids receive the generated renewable energy and pay for them at good rates. The FiT policy also equates to guaranteed grid access and long-term contracts.
- Large Scale PV power plants
- Basic information
- Data on number of plants in the US
The advent of PV in the public domain has resulted in the rapid reduction of system prices in the last few years. Earlier, PV systems were limited to households and businesses. However, that has also changed and large power plants are now adopting PV systems on a major scale. Currently, there are scores of large scale PV power plants operating from different parts of the world. Europe is well known for the wide usage of PV systems and also has a lion’s share of large scale PV power plants. This trend has now spread into other countries like the USA and China driven by their respective governments and incentive programs. The PV technology available today is quite versatile and robust and suits the needs of different types of PV systems owners including large scale PV power plants.
An interesting tidbit is that 1/3rd of the world’s surface is covered by deserts. If solar PV systems were to cover even 4% of this surface, then the world’s energy consumption would be taken care of since the annual energy production from solar PV systems would be more than enough to cater to the planet’s electricity demand.
Even more encouraging is the fact that researchers are now able to forecast the affect of cloud cover and weather on large scale PV power plants. This is a very positive development since it heralds the way for better understanding the power fluctuations and the method in which they can be stabilized greatly.
Performance and Efficiency
Insolation: It refers to the exposure of an object to the sun’s incoming rays. Essentially, it is related to the solar radiation that is received and the rate of its direct delivery per unit of horizontal surface. Net to net, it deals with the total solar radiation.
Inverter: Solar PV systems operate by transforming direct current (DC) into alternate current (AC). The energy is provided by the sun itself and is received by solar PV panels. The conversion however of DC into AC is done by inverters. An effective inverter can facilitate production of output in the utility grid with minimal harmonic distortion. This essentially allows the operation of even the most sensitive electronic devices. Inverters when chosen well can mean low standby losses, good reliability, easy servicing and low harmonic distortion.
Battery Packs: The main purpose of batteries or battery packs is to store accumulated solar energy generated by PV systems. The energy thus stored can be used at times when the energy input is either low or is not available. A typical example is solar energy that is unavailable during nights. An additional advantage of battery packs is that they can discharge quickly and therefore yield more current (when compared to the charging source). This can effectively be used to power pumps or motors intermittently. There are various types of battery packs that can be used for PV systems. However, the most popular and effective is the lead-acid batteries.
Benefits and Barriers
Sunlight is free and abundant. Moreover, some part of the world is always facing the sun. Therefore, it is available on a 24×7 basis. As such, PV systems are the best type of energy that we can rely and bank on.
It is also a preferred source of energy considering that it produces absolutely no pollution and is thoroughly in sync with nature. Further, there is no hazardous waste produced through solar energy as is the case with coal and nuclear powered energies. To top it all, it doesn’t require any fuel to either be transported or combusted like water, gas or coal.
Global Warming: Solar energy ensures that there is no contribution to global warming since it is clean and natural energy.
Green house gas reduction: The energy generated through PV systems is completely free of green house gases which is not the case with other conventional sources of energy. Therefore, by enhancing the usage of solar energy, the world can actually reduce the green house gases and make Earth a cleaner planet.
Conventional fuels: Solar energy is a sound investment for the future since it is growing by leaps and bounds. In fact, it is an unlimited source of energy since it is estimated that the sun will last for a long long time to come. This is a definite plus when compared with conventional fuels. The latter are expected to run out in the near future – some of them perhaps in our own lifetimes. Solar energy therefore is clean, unlimited and is thoroughly in sync with nature. Further, there is no hazardous waste produced through solar energy as is the case with coal and nuclear powered energies. To top it all, it doesn’t require any fuel to either be transported or combusted like water, gas or coal.