Thursday, April 20, 2017

Solar Power



For many people, camping and caravanning are about ‘getting away from it all’ and not being tied down – even to an electric hook-up point. Add to this the cost of a nightly electrical connection and the fact that many of us like the idea of reducing our use of fossil fuels (both through the national grid or a petrol-powered generator) and solar power seems to have much going for it.

There are several ways of using the sun’s power to make life easier for camping. Solar showers have been on the market for many years. They generally have a black container that you fill with water and leave in the sun to heat up. It’s then simply a case of letting the hot water out of the bag through a shower head. This is a cheap way of using solar power and is replicated in more sophisticated installations for houses, where solar panels (for example: Renogy 150 watt solar panel ) on the roof contain water that heats up and in turn heats the water used inside the home.

However , solar power from photovoltaic (PV) solar Power, energy and capacity probably fits more easily into our camping lives. Here the sun’s energy is converted into electricity in the panel. This can be stored in a leisure battery and released again when we turn on an appliance.

Power in watts (W) = current in amps (A) x voltage in volts (V)
Energy in watt hours (Wh) = power in watts (W) x time in hours (h)
Battery capacity in amp hours (Ah) = energy in watt hours (Wh) / voltage in volts (V)
Choosing the right panel for you

Finding the right solar panel for you can be a challenge. Unfortunately, some people are put off solar panels because they buy the wrong one. Too low an output and you’ll find you’re running out of power. Or you could spend a large amount on a top-of-the-range set up and only be using a small proportion of its output, making it seem excessively expensive.

One straightforward way to find the type of solar panel that’s right for you is to go camping with a fully-charged battery in your unit, don’t connect to an electric hook-up and see how long your battery powers your appliances.

When you return home, find the rating of your battery (it should be marked in amp hours – Ah) and calculate the average energy you’ve used during your trip. For example, if a 110Ah battery has lasted for two days, that’s an average of 110/2 = 55Ah per day. This is a slight over-estimate because you’re unlikely to use the whole of the battery’s capacity before your TV stops working or the water pump fades, but it gives a rough guide.

You’ll therefore be looking for a solar panel to top-up your battery by a similar average, in this case by 55Ah per day – remembering that any solar panel will only be topping up your battery when sunlight is falling on it.
Calculating your power use

If you don’t have the opportunity to check your real power consumption on site, you’ll need to estimate it using the power ratings given on every piece of electrical equipment you plan to power from your battery.

In electrical terms, power (measured in watts, W) equals current (in amps, A) multiplied by voltage (in volts, V). Y our battery produces roughly 12V to power your equipment, so to work out the drain on your battery from an appliance, take its power rating and divide by 12.

For example, a 16W light draws a current of 16/12 = 1.33A. Turn it on for three hours a day and you’ll need 1.33 x 3 = 4Ah every day from your battery to power that single light.

Use a 45W 12V television for the same time and you’ll need 3 x 12/45 = 11.25Ah every day from your battery.

Top tips

If you use a crystalline panel, don’t forget that even the shadow of a thin wire can make a difference to the power output. Make sure as many cells as possible are in full sun.
Solar panels will work behind glass, but with limitations. They are designed for direct sunlight, so if you put a panel behind glass or a plastic window its efficiency will be reduced. It may take up to three times as long to provide the same charge to a battery if you put the panel behind a window, even if it’s in full sun.
Connecting a solar panel to your leisure battery may be as simple as attaching a couple of clips, but some caravan and motorhome manufacturers provide specific adaptors so it’s worth checking with your local dealer before you buy a new panel.
If you invest in a solar panel, make sure it’s positioned to take advantage of the midday sun, which is the strongest. This is almost directly overhead in summer, but lower in the southern part of the sky at other times of the year. Angling your panel towards the sun will increase the energy it generates outside of the summer months.
Some solar panels are portable and come with all the connectors required to attach them to your leisure battery, such as the Solar Technology 4W Fold-Up panel. Others can be permanently secured to your unit and may come packaged with a suitable fixing kit. Before you buy, think about how you will use the panels (including whether they will normally be positioned in full sunlight), whether you want to have them permanently fixed and if the attachment points may affect the water ingress warranty of your unit.
The power you generate from your solar panel will only be as good as the condition of your leisure battery, so it’s worth looking after your battery. The Club has another Data Sheet – Looking after your leisure battery – to help you do this.
The power generated by a solar panel is direct current (DC), so if you want to use it to power something that would normally plug into a home-style three-pin 230V socket you’ll need to convert it to alternating current (AC). For this you’ll need an inverter.
A solar panel can be ideal for keeping your battery topped up during winter storage, especially if you have a caravan or motorhome with a battery-powered alarm system. To take account of the low light levels in winter you may need a 20W panel or more.