More and more people are opting for solar panels on their roofs. This is a logical trend, because solar panels are not only good for the environment, they also provide substantial savings on your monthly energy bill. But how do solar panels actually work?
Solar panels consist of solar cells that capture daylight and convert it into direct current. Because direct current cannot be used in a home, solar panels are always equipped with an inverter. This inverter converts direct current into alternating current, so that the power is ready for use. If you generate too much solar energy, you can feed it back to the grid. Solar panels are also called "PV panels", where "PV" stands for "Photo" (light) and "Voltaic" (electricity).
Solar panels nowadays have a service life of at least 25 years. As solar panels get older, the yield decreases slightly. Most manufacturers give a yield guarantee stating that the solar panels will still give a minimum guaranteed yield after 10 and 25 years. This gives you the guarantee that your solar panels will still be working properly after a number of years. The power of solar panels is expressed in Watt peak (Wp). Most solar panels in Belgium have a capacity of 350 Wp.
With solar panels you are not only choosing a sustainable solution, you are also saving on your energy costs. The exact yield from solar panels varies from one situation to another. Your energy consumption and the location of your roof determine the savings, amongst other things.
In Belgium, the guideline is that when renovating, the panels pay for themselves in about 7 years, although this period varies more at the moment because energy prices are not stable. In the case of new builds, the installation of solar panels is compulsory on the one hand, but it always makes sense with a payback period of around 9 years on the other.
A solar panel system does not require much maintenance. Checking and cleaning the fans of the inverter annually can do no harm. The panels themselves are theoretically self-cleaning.
If the panels are relatively flat, dirt can accumulate and cleaning them with water and a mild detergent is certainly not a bad idea to improve efficiency. The same as washing windows.
Flat plate collector:
- In a flat plate collector, sunlight falls on a metal plate that is covered with a special layer which absorbs almost all of the sun's radiation and converts it into heat.
- Behind this plate, a liquid flows in a tube, which absorbs the heat and transports it to the boiler tank.
- Insulation on the back of the absorber and a glass plate prevent heat from being lost. The whole forms a flat plate collector.
Vacuum tubes:
- This collector is composed of a number of adjacent glass vacuum tubes. In each tube of such a collector there is also a metal plate, like the metal plate of a flat plate collector.
- Because this plate is in a vacuum, this collector has very low heat losses, which means that this collector has a better efficiency all year round.
- Because this plate is in a vacuum, this collector has very low heat losses, which means that this collector has a better efficiency all year round.
- A solar water heater heats water with energy from the sun. The solar energy is collected via a solar collector that is (usually) placed on the roof. In the solar collector a fluid circulates that transports the heat from the collector(s) to a storage vessel or boiler.
- The storage tank ensures that the solar heat can be stored. The heat can then also be used at a later date. Sufficient storage volume is therefore recommended (e.g. 300 litres for a family of 4).
- In most cases, an after heater is also provided. If there is too little sun, the back-up heater can ensure that the water is brought up to the desired temperature. In most cases, the central heating boiler takes care of the reheating function.
- Even on a cloudy day, the solar water heater will produce heat. In Belgium, a solar water heater can produce up to 60% of the hot water needed and ensure that you wash for free for most of the year.
Solar collectors perform best when they face south. If they face east or west, the efficiency of the solar system drops by 20%. Those who choose vacuum tube collectors can solve this simply by turning the tubes towards the sun. The ideal angle of inclination for flat plate solar collectors is 45°, but any angle between 20 and 60° gives good results.
Vacuum tube collectors have the advantage that they can also be mounted horizontally on a flat roof and individually rotated until an angle of up to 45° is reached. Vacuum tube collectors can also be installed vertically on gables or the balcony support of a flat.
The collector surface and the capacity of the storage tank must be matched to the hot water requirement and consumption pattern. A good rule of thumb is that for a consumption of 40 litres of hot water at 50 °C per day and per person, you should install approximately 1.1 to 1.5 m² of solar collectors. The price of a solar heating system obviously depends on various parameters, but a guideline price for a complete system is € 1000 per m² of solar collectors, including installation. This is indeed an investment, but this basic investment is often made a lot lighter by premiums for a solar water heater:
- In Flanders: 550 euro/m² solar collector, with a maximum of 2,750 euro or 40% of the invoice amount.
- In Brussels: The premium for the installation of a solar water heater in the Brussels Capital Region varies between € 2,500 and € 3,500, depending on the income category and the location of the dwelling, up to a maximum of 50% of the invoice amount.
- In Wallonia: The premium for the installation of a solar water heater in Wallonia varies between € 750 and € 4,500, depending on the income category, maximum 70% of the invoice amount.
- Solar thermal collectors are a good solution for making use of the free energy from the sun.
- On an annual basis, you can save up to 60% of the energy needed to heat the water for your bath, shower or kitchen.
- In addition, you can also use solar boilers as (auxiliary) heating for your home or to heat your swimming pool.
- With rising electricity prices, this can provide a lot of comfort for a relatively limited price.
A solar installation is very maintenance friendly. Only the transport fluid needs to be checked periodically.
Specific maintenance activities:
- The anti-freeze tester is used to check the frost resistance of the fluid in the solar system. If the measurement is carried out at room temperature, you can immediately see to what degree the system is protected.
- A precise method is to measure with a refractometer. A refractometer determines the frost resistance on the basis of the refractive index. A few drops on the glass are sufficient to read off the freezing temperature. Solarmedia are available in different compositions. The refractive indices can differ slightly. To ensure an accurate measurement, you should consult the data sheet for the medium.
- If you have selected an empty system or a system with thermal steam protection, this is not necessary.
