Getting Started in the big Solar Challenge

The great thing about starting with this solar challenge is you do have a number of options, you can have a complete system with all the bells and whistles or you can simply put a toe in the water with a very basic system and see how it works out for you, below we can look at some of the choices available to you:-

Option 1
A complete professional solar system installed *On Grid with hot water providing electricity and up to 50% of your hot water energy. **Approximate budget needed £10,000 - £15,000

Option 2
A complete professional solar system installed *Off Grid with hot water providing electricity and up to 50% of your hot water energy. **Approximate budget needed £8,000 - £13,000

Option 3
A complete professional solar system installed *On Grid. **Approximate budget needed £6,000 - £9,000

Option 4
A complete professional solar system installed *Off Grid. **Approximate budget needed £4,000 - £7,000

Option 5
A complete professional solar hot water system providing up to 50% of your hot water energy. **Approximate budget needed £5,000 - £9,000

Option 6
One or two solar panels for a partial energy saving exercise. **Approximate budget needed £500 - £3,000

Option 7
One or two solar panels for an outhouse, extension or conservatory. **Approximate budget needed £500 - £2,000

Option 8
One or two solar panels for a workshop, garage, shed or greenhouse. **Approximate budget needed £300 - £700

For the smaller partial systems in extensions, conservatories, outhouses, workshops, sheds and greenhouses it is possible to do the job yourself providing you are suitably qualified and have good practical skills. Do not however be fooled into thinking that just because these systems are 12/24volt systems that they are not dangerous, because they can be far more dangerous than a conventional electrical installation. If in any doubt as to your own ability consult a qualified electrician, this does not mean that you cannot make a saving as you can still work with your qualified electrician in managing your installation. There is a lot you can do with the right practical approach, this website will in any event give you a good idea as to how your system works and will only add to the job at hand even if you are having it professionally done.

* On Grid means being connected to the mains and selling any overflow power to the electricity companies, whereas Off Grid is not having this facility.

** This figure is offered only as a very rough guide as property sizes and location can make very big differences.

Warning - Do not however be fooled into thinking that just because these systems are 12/24volt systems that they are not dangerous because they can be far more dangerous than a conventional electrical installation. Please read the various pages on battery care and maintenance carefully and take note of the precautions necessary in the solar challenge.

If you are having your system professionally installed then you will have a consultation and specification supplied by your chosen supplier. But if you are doing the job yourself or with a qualified electrician you need to look at what your needs are and do some very basic calculations.

Example Solar System and the working out

Lets look at a basic system for a 1 roomed extension with two table lamps a TV and receiver (all 12 volts appliances). You can of course run your normal household appliances but you will need an inverter and the figures below would have to be adjusted for the extra power needed.

The first consideration is the ability to be able to mount a solar panel facing south with as much uninterrupted sunshine as possible. Next we must consider the housing for the storage of leisure batteries, this could be in a sound waterproof workshop, garage or similar dry storage facility. Read the looking after your leisure batteries page.

Having settled on those two points the next thing is to do some sums to determine the solar panel size and the number of batteries required.

Lets look at the power requirement in detail (these are all examples only - check the labels on your own appliances):

We can use some Ohms Law here to help us work things out!

Appliance

Current (Amps)

Hours on

Amp Hours

Table lamp 12 volts	2 Amps	5 hrs	10 Ah's
Table lamp 12 volts	2 Amps	4 hrs	8 Ah's
TV	2.5 Amps	3.5 hr	9 Ah's
Receiver	3.3 Amps	3 hrs	10 Ah's
			____________
Total amp hours			37 Ah per day

To be able to service this energy requirement it would be advisable to have two 85-110 amp hour leisure batteries. Although the figures indicate that one battery would have enough standby power, you would be running a single battery down to a very low point where permanent damage could be done as batteries do not like being run down as low as to 50% of charge. So two batteries would be best so they can both share the load. This way the batteries should have a very long life. See looking after your leisure batteries.

Now lets look at the solar panel(s) size necessary to maintain the correct level of charge per day i.e. replacing the 37 Ah's we have taken out and having enough extra power to keep the batteries fully charged even on the darkest of days. For the sake of this example I am assuming that during the darkest months of mid winter we only get 4-5 hours of good collectable light. Therefore to replace this energy we would need two 125 w solar panels which would each supply 20.5 Amps per day during the 4-5 mid winter hours equalling around 41 amps in total for the two panels. This covers our 37 Ah per day with a bit extra to help keep the batteries topped right up to the top. The sizes of the solar panel would be approximately 1500 x 700 x 35 each. This equally could be achieved by having multiples of smaller panels to the same value of 250 w output, this option often makes it possible to fit arrangements of panel sizes into a given space. It is very important to us all that the panel arrangement looks neat and well balanced from an aesthetic point of view as the panels are often viewable by neighbours who may have it as their only view all day.

Here is the working out in simple terms:-


Energy requirement = 37 Amp hours per day

Battery storage requirement = 2 x 85-110 AH batteries

Solar panel(s) = 2 x 125 watts giving 41 Amps per day (winter hours)

It is worth pointing out at this stage that for a very large part of the year the above system would be producing far in excess power than we actually need, so additional appliances can be added as long as you monitor and manage your batteries carefully during the mid winter days. See the batteries page. Managing your energy needs is largely about storage and storage means batteries. The more batteries you have the more disposable power you have and the longer you can continue with your energy requirement level on the worst light level days. Your system should be specified to always have some reserve energy, only having enough energy to just about skim through can cost you dearly later in terms of replacement batteries.

Buying 12 volt Appliances:

You can purchase a good range of table lights, plugs, sockets and electrical fittings from sailing chandlers and caravan/motorhome accessory showrooms, you can also convert your existing lamps by changing the mains plug to a 12 volt plug and putting a 12 volt bulb and new bulb holder in place. There are types of bulb we are all familiar with that are 12volts and screw into the edison type bulb holder. IMPORTANT - You MUST of course still change the 13 amp plug for a 12 volt plug.

Please note:
Always read all of the pages on this website before starting a solar system installation - especially the solar wiring page.

Other pages to help you with the installation are:-

	How to wire up a basic solar panel system Is your battery bank correctly wired up?
	All About Inverters in a solar system
	The Big Live Solar Panel Experiment See how our 27w solar panel performs under live conditions
	Battery care
	Looking after a leisure battery
	Solar circuits and solar power circuitry
	Choosing and using your wire in your solar system Always read the page above before starting a solar installion.

To communicate with us over technical issues please use the Solar Chat Forum, also take a look at the Solar Q&A page.



© Copyright 2008 - all rights reserved

---

Global Warming - it's why we are making changes to our way of life!

David Bellamy has a very interesting article on global warming where he gives another point of view, Read the article