What Is The Lifespan?

Q: How long do photovoltaic (PV) systems last?

A: A PV system that is designed, installed, and maintained well will operate for more than 20 years.  The basic PV module (interconnected, enclosed panel of PV cells) has no moving parts and can last more than 30 years.  The best way to ensure and extend the life and effectiveness of your PV system is by having it installed and maintained properly.  It is estimated that performance will decrease by under 1% per year, which would mean that in 50 years they’d still be 60% efficient, but nobody really knows past the guarantees given.

Experience has shown that most problems occur because of poor or sloppy system installation. Failed connections, insufficient wire size, components not rated for dc application, and so on, are the main culprits. The next most common cause of problems is the failure of the electronic parts in the balance of systems (BOS): the controller, inverter, and protection components. Batteries fail quickly if they’re used outside their operating specification.  For most applications (uses), batteries should be fully recharged shortly after use. In many PV systems, batteries are discharged AND recharged slowly, perhaps over a period of days or weeks.  Some batteries quickly fail under these conditions. Be sure the batteries specified for your system are appropriate for the application.

Q: What happens if something goes wrong?

A: All panels come with a 20+ year performance warranty so in the unlikely event that you experience problems, the supplier should be on hand to diagnose your problem and if necessary, arrange a home visit to ensure that everything is working as it should be. The installation comes with a 5 year warranty so you can be sure your service will be of the highest standard.

Q: What maintenance and cleaning do the systems need?

A: Solar photovoltaic systems are silent in operation, have no moving parts and require no maintenance.  Solar thermal systems have a few moving parts (inside the pump) but these are virtually maintenance free, you may need to replace the anti-freeze in a solar thermal system after about five years.  Most of the time the rain will keep the modules clean.  However, a build up of dirt can affect system performance.  The degree of soiling will depend on the location but usually dust accumulation and self-cleaning reach a steady state after a few weeks if the array tilt is at least 15 degrees. In extreme cases dust may cause a power reduction of about 10%.  At low tilts horizontal glazing bars can trap debris which could lead to shading of part of the array. The design of the system should aim to minimise uneven soiling.

The modules can be cleaned with either a hose or, if possible, soapy water and a non abrasive brush.

Q: Doesn’t the glazed front reflect light away from solar photovoltaic (PV) modules?

A: Not really, no.  Solar PV modules constructed with a glass front have two characteristics that reduce light reflection.  In order to optimise electrical yield the glass is treated with an anti-reflective coating which greatly increases the transmittance through the glass so to maximise the amount of light reaching the solar cells.  Secondly the outer face of the glass has a slight granular texture.  The result is a matt like finish rather than a mirrored, again this is actually intended to maximise yield.  These two characteristics greatly reduce reflection from the glazed front face of solar PV modules when compared with conventional glazing.

Q: Will I ever have to go without power?

A: Your home will still be connected to the National grid.  If at any time your solar panels are producing less electricity than your home is using, or at night time, you will just receive electricity in the normal way.  Only if there is a power cut will you not be able to generate electricity.

Q: How long do PV systems last?

A: A well-designed and maintained PV system will operate for more than 20 years. The PV module, with no moving parts, has an expected lifetime exceeding 30 years. Experience shows most system problems occur because of poor or sloppy installation. Failed connections, insufficient wire size, components not rated for dc application, and so on, are the main culprits. The next most common cause of problems is the failure of electronic parts included in the Balance of Systems (BOS) – the controller, inverter, and protection components.

Q: When will solar electric systems replace coal and nuclear power plants?

A: Right now, our nuclear and fossil-fuel-based energy is quite inexpensive compared with the cost of solar energy. Oil and coal prices are low in most places, so solar energy still can’t compete on a first-cost basis in many regions of the world, such as the United States. As this situation changes, we’ll begin to see many more solar energy systems being built in areas that now use fossil fuels and nuclear energy for electricity generation.  In the UK the government has committed to 10% renewable energy production by 2012, and 20% by 2020.

Another driver in the deployment of solar systems is public demand for clean energy. Fossil-based energy pollutes the environment, and nuclear energy creates hazardous waste. If we stop to consider the environmental and health costs of fossil-fuel and nuclear energy, then solar energy already makes sense today.

However, in developing countries where there is little or no supply system for conventional energy, solar energy is being used more and more. It can be much less expensive than many other options, and the environmental benefits associated with this cleaner form of energy are significant. In developing countries, the key barriers to wider use are the need for financing and for electric distribution networks.

Q: When will I be able to buy a solar electric or PV-powered car?

A: Because most automobiles are very heavy and aren’t very efficient, it would be very difficult to power one with solar cells. But if a car were built specifically for PV, it could provide suitable transportation. As we’ve seen in many student-built vehicles for competitions, solar cars are very light and efficient and have enough battery storage to travel for miles on a cloudy day or at night. Solar cars can travel the speed limit on normal highways, but only as long as the sun is shining or until their batteries run down.

A more realistic car would be another kind of electric vehicle, one that many companies are working on right now. These cars could be charged by solar panels during the day, for example, while people are at work. They could also be plugged in at home for charging when the sun is not shining.

The benefits of solar cars are obvious: they don’t pollute, and free sunlight is their fuel. The drawbacks are that, using today’s technology, a solar car has to be very lightweight for the panels to provide enough energy to power the car at road speeds, and it has to have enough battery storage to travel long distances without sunlight (e.g., at night and on overcast days).

As part of continued research and development, many organizations are improving the systems used in solar cars to make them more efficient and cost effective and thus more widely used (the systems, anyway). Wider use of solar electric cars (or other electrics) probably depends on the availability of inexpensive, lightweight, compact energy storage methods. Car companies are making great strides in this area with the new gas/electric hybrids, and future progress is likely to be rapid.