Photovoltaic (PV) Solar Panels in Buildings And Homes - An Overview
Posted on Sep 04, 2008 - 02:19 AM
By: Jayanth Krishnappa
A solar cell or a photovoltaic cell made of a semiconductor material, typically silicon, converts the sun’s radiation into usable electrical energy. Multiple cells are connected electrically to form a PV module, otherwise known as a solar panel. These modules provide versatility in terms of the energy output required for the intended application. This modular property of PV systems makes it a feasible power source for a small calculator to something as big as a centralized power station. It is now a common knowledge that this, once exclusive space technology is being implemented in everyday life due to its environmental benefits and to address the energy crisis. Studies suggest that the electrical energy produced by a square meter of solar panels can effectively displace an excess of two tonnes of CO2 emissions to the atmosphere over its life time. Buildings are known to contribute over 50% of the global green house gas (GHG) emissions. Therefore, PV is clearly a green step towards environmental sustainability if implemented in buildings.
The wide spread application of PV solar panels in recent years has certainly proved that it is a viable technology even for a basic household. The next concern however is the economics. Photovoltaic systems are considered to be a sensible investment, be it for an ordinary householder or the commercial and industrial sectors. The two main reasons are future energy security and contribution towards protecting the environment, which are both vital. Apart from self benefits, there are policy issues which play a part. Climate change is driving the move towards carbon taxes that will make energy more expensive. As already introduced in most countries in the world for the industrial and commercial domains, these taxes are expected to extend to the lower levels of the society in the near future.
Selecting your PV solar panel system:
There are different types of PV systems available which are capable of varied levels of performance (efficiency and output capacity) and their cost varies correspondingly. You have to choose the system which suits your own energy needs.
The first step would be, to recognize the type of current output required. i.e. the equipments may run on DC/AC power. Since PV modules generate DC power, there is a need to convert it to AC using an inverter in most cases. When this is sorted, the next step is to choose the right system.
- The two basic categories of PV systems are the
- Stand – alone system and
- Grid – Connected system
Stand – alone solar panel systems are preferred for installations on remote sites which have no utility grid connectivity. The power generated by the system is wholly used on-site or partially stored for consequent utilization.
Grid – connected solar panel systems generate power for on-site applications and are also capable of supplying surplus power to the utility grid. Metering devices record the energy supply enabling you to earn the payback on your investment.
After you have chosen the type of system, the average sunlight hours per day has to be calculated for your location. The data can be found from the regional meteorological (MET) center or can be roughly estimated by observation. By knowing the power output of a single Photovoltaic module and the number of hours it is possible to generate power, we can estimate the total energy output over a period of time. A key factor is the positioning of the solar modules in order to get an un-obstructed exposure to sun light. The angle of inclination is also a consideration if the panels are being installed on a flat surface.
In order to match the supply, the energy demand in the household or any installation in general has to be estimated. An energy budget chart can be prepared to calculate the total energy consumed over a day and try to estimate how many PV modules can supply the average demand (In stand alone systems the peak demand is to be considered). A suitable range of inverter has to be selected for AC applications. And of course the regulatory issues have to be sorted out with the local Utility if it is a grid connected system.
There are many professional organizations or commercial enterprises who can provide solar panels, system sizing and installation services. But it can be done individually and get the estimation validated by a good supplier, which in most cases is offered readily. A number of sizing tools are also available on the internet which are accurate enough for small installations; nevertheless the estimation can be validated by a supplier. Once installed the solar PV modules require very little maintenance apart from keeping the surface of the collectors clean. Manufacturer warranties for modules range from 15 to 25 years and up to 30 years in some cases.
The cost of installing a solar panel system has been coming down over time due the phenomenon of economies of scale seen in their manufacturing. Considering the energy cost rise for the next ten years, it is a worthwhile investment. Typically PV systems earn their payback over 10 to 12 years in case of a household installation. However this period may well be diminishing due to the rate of rise in energy costs.
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