Using solar energy in the uk is not a new thing, it has been done for several years. It has been used mainly in remote locations where power is not available or in places where cost of getting power to the utility is too great. However in recent years, particularly in the last 3 years, many new applications of solar can be seen, such as remote weather transmiters alongside roads, warning signs and various other applications. There has been increased pressure on the european government to bring in a law (that still needs approving yet) to build all new houses with 10% of their own power generated by wind or solar. Already along the M27 between junction 8 and 9, there is the first south west motorway installation of solar energy, with a 11kW solar pannel array (which can be seen from the motorway when driving).
I have built this web page to help people understand both the practical and theoretical issues of using solar and wind energy. This web page will slowly be updated as people ask me questions.

Is wind power too noisy?
This is a common misunderstanding, wind generators do make some noise, but so do cars and virtually everything that moves. Also industrial estates make quite alot of noise, even at night, but no one seems to mind! There are many new wind generators now which have a noise level of less than someone walking along the road, for example the 'Whisper' and 'Swift' wind generator which are well suited to domestic low noise applications.


Can Solar Pannels Generate Sufficient Power in England?
Yes. Solar power can generate sufficient energy to power a complete house off grid and even to sell it back to the grid. Many people in the UK have done this (although it hasn't been well documented), for example CAT - Center of Alternative Technology, based in Wales, they have enough power to run an entire center and also to sell back to the grid.
The misunderstanding comes from what the general public see as solar pannels, for example you can buy for about £20 pounds a solar pannel designed to trickle charge a car battery, well i have tried it and it doesn't even light an LED (20mA)! Any solar pannel less than about 80W are usually intended for very low power applications and often with efficiencies of 7%-10% or less, ie for every 1000W of solar light only 70W is possibly converted. However, the industrial pannels starting at about 80W and going up to typically 200W, these can generate some serious power, and when configured into an array, then it can generate several kilowatts of power, sufficient for an entire house. It is generally good to complement solar and wind together.

The following describes some issues you may wish to consider when deciding which type of system to install.

PLEASE NOTE: Although i have layed out some basic points, i strongly recommend that if anyone decides to install a kit or any form of power generation equipment, check with an approved and qualified electrician that all the regulation requirements have been satisfied in the installed equipment and all wiring is complient with current safety standards.
Unfortunately tonight i have just heard on the radio that by the beginning of year 2005, there could be a new law in the uk, banning anyone installing their own electrics. I don't know if this only applies to grid tied installations or not, but this needs to be carefully looked at if you are thinking of installing your own system. I will be updating this web site as when i know more.



1. How to size up your system.
The first issue that needs to be evaluated is 'Sizing the System'. Independant of whether you are installing yourself or using a company to install, sizing the power requirements is needed to evaluate how much power is required to be generated.

Calculate the kWh power required for each applience.

example
	a) 1000W hairdryer used for 1 hour
	=> 1000 x 1 = 1000WattHour (1000W=1kW)
	b) 500 flood light used for 40 min
	=> 500 x (40min/60min) = 333WattHours = 0.33kWh

alternatively use this calculator:

Energy Required by Applience
Enter the applience power (watts)
Enter time applience is on for (mins)
Energy Required From Solar Pannels
Power in kWh

2. Which way now?
There are three methods of installing.

a) Professional installation.
If your not particularly technically minded, then this is probably the best option. A few things to think about.

• Firstly, only go to a governement approved installer. There are government grants available (up to 50% grant), but these are only available for government approved installers.
  
• Secondly, usually most reputible companys will sort out all the planning permission side of it (if its needed, especially for wind generators). With solar pannels there is no planning permission required (as far as i know*).
  
• Thirdly, before signing up with the company, ask for references of people who have had their installations. Unfortunatly, there are a lot of tom-dick-and-harry type people who take full advantage of 'quick' installations.

b) Kit Installation.
Some companies sell solar panels in kit form, complete with frames, batteries, cables, inverter, chargers etc. This can be a good options if you have a reasonably good working knowledge of wiring, and some technical understanding of how electrical installations should be fitted. Note that all installations, if connected into the house ring main etc, must comply with british standard IEEE regulations, earth bonding and cable installations*. It may be worth buying the kit and asking an approved contractor to install it. The disadvantage of this, is that the government grants (as far as i understand it*) are not available and the kit will be taxed at the standard 17.5% VAT. The grants are only available* if the system is completely installed by the governement approved companies (this is usually only found out in the small print!). This is the same as the VAT issue. For full system installation, the VAT is reduced down to 6% or so* on governement approved installers.


c) Home Installation.

This is the option I have taken. The only reason i have done it this way is so that i could learn how the system works and actively monitor solar irradiation and wind power. The home installation is definately the more exciting option, giving the maximum flexibility of performance, requirements and efficiency. Usually the limiting factor on this is the cost. Below are the technical details of i have gathered along the way.

The reality of installing it yourself, is that it is expensive and can be quite time consuming, however, the great advantage is that if something goes wrong, you will know exactly what it is and how to fix it. It also provides good flexibility to update at a later time, for example the batteries or increasing the capacity of the solar panels or wind generators.



3. Technical Information
Here are some tips i have picked up along the way.

Solar Pannels

• There are many different types of solar pannels available today, ranging from Kyocera, Sony, Shell, Philips, Uni-Solar.
  There are also different types of solar panels with different silicon growth micro archetecture. Details on this is not necessary because as soon as the power is greater than about 75W, it all amounts to generally one type.
  
• The pannels i have used are the Kyrocea KC125. These are 17v 7.35Amp each, and together generate up to 14 amps. In reality, most people use either 80W, 100W, 120W and 150W. Sometimes it can work out cheaper to get a bank of 80W than the same power but in 150W panels. Also to consider, if someone throws a stone at an 80W pannel and it breaks, its cheaper to replace than a 150W!
  
• Usually solar pannels include a bypass diode (these are diodes which allow current to bypass the solar pannel if one is shaded and the others not.) This information will be supplied in the specification of the solar pannel.
  
• Usually solar pannels are wired in parallel banks, connecting through a 'connector box' or 'disconnect'. For high power installations, all power should be able to be isolated, so a disconnect should be inserted at the output of the pannels.
  
• Don't forget that all the solar pannels and racks need to be earthed! You may require a separate earth rod for this.*
  
• For optimum performance, the panels need to be carefully angled with the sun, there are calculators available for this on the net, check out some of the links. If your flush mounting them on the top of the house roof, the angle is not so easily changed. If you choose free standing (as i have), the array can be arrange at any angle (and optimised). I brought a metal post from a local metal merchant, then brought the frame from Uni-Rack (Uni-Rack mounting i have used (datasheet))
  
  
  Solar Chargers
  There seems to be a lot of them around! There are many different variations of solar chargers. I have used the Steca Solsum 8.0x Charger (Datasheet). These are pulse width modulated chargers. The idea is that the solar pannels are considered as constant current devices, that means that the voltage will vary, but the current will remain the same. The charger will pull the current out for any voltage, and invert it up above the battery voltage in order to charge the batteries, ie if the battery voltage is 12.58v, then a voltage of 12.54 volts will not charge it, so the charger will take the open loop voltage up to about 14.0v, thus forcing the batteries to charge (this is the simple basic outline). There are other chargers available, but i would advise to use Pulse Width Modulated (PWM) based chargers if possible. If your looking at higher powered based systems, eg 1kw and higher, the company 'Trace' (cream of the cream) make excellent charger/inverter units, very expensive, but boy, they look after the batteries well!
  Some chargers (eg about £100 for a 20Amp charger) will display battery voltage, current discharge/charge, status and with the addtion of temperature compensation etc. If you have no means of normally measuring the voltage, it may be a good thing to have a visible read out of the battery voltage to give you an idea of the current power storage in the battery bank. Remote display units are also available to view from the house.
  
  
  Inverters
  The inverter is one of the key parts to the system. If this is wrong, then it may end up wasting alot of the investment in quality chargers, batteries etc.
  The inverter converts 12v DC up to mains 240v AC 50Hz (variations are 24v DC, 110v AC, 60Hz and also 3-Phase). The output will drive standard domestic appliences.
  There are two types of inverter, the 'Modified Sinewave' and 'True Sinewave', difference being the shape of the output sinewave.
  Note: do not mix grid tied electrics with off-grid electrics unless it passes through a grid-tied inverter/connection.
  
  'Modified Sinewave'
  The modified sinewave is basically another way of saying mains voltage, but with a square wave output. The advantage of this, is usually they are cheaper and much more efficient (as the internal transistors are operating in cut-off region not active mode, with high frequency invertion). They are ideal for lights, heaters and any non-sensitive equipment, but not suitable for tv, hi-fi, dvd players etc. Another point, is that if the inverter is a long way away from the house, then because it is square wave, then it is made up of lots of different frequencies of sinewave and co-sine waves (mathematicaly modeled by the fourior series), the practical side is that it could end up transmitting into the air interference waves which could interfere with the neighbours tv and radio sets (and ultimately could cause problems if traced).
  
  'True Sinewave'
  The true sinewave inverter is the preferred type, the only real disadvantage with this is the cost. The output will be a true sinewave, with no harmonics. This is suitable to all applications and is identical to the mains electriciy. I have used a true sinewave inverter so i can power my tv, hi-fi etc and with no transmitted radio interference from it.
  
  Inverter Tips
  Some points to look out for when buying an inverter.
  
  • Efficiency, the newer ones are typically about 91% (AJ201 example inverter from Morvan).
  • Quiescent power, this is the amount of power used by the inverter when no load is connected to its outputs. Beware the cheaper inverters usually have quite a high value here.
    
  • Usually the inverters have built in fuses, low battery voltage alarm, output protection etc.
    
    
  Note:
  POWER (WATTS) = VOLTS x AMPS
  example
  so if the Load = 300 Watts, then
  Amps = Power / Volts => Amps = 300 / 240 = 1.25Amps @ 240volts
  so
  Ratio of transformed current = Vo / Vin x Io
  so 240 / 12 = 20, therefore input current would be 20 x 1.25 = 25A
  so in this example, for a 300W load at 240volts, it would require 25Amps at the input of the inverter at 12v DC.
  
  From this example, you can see that if you load is eg 2kW, then you would b require 166Amps, which means big batteries, big cable and big inverter, with big money! However a wind generator could supply a large amount of this. Eg if its a 1.5kW wind generator, then this would supply 1500/12=125Amps instantaneous (although in reality i have been told, that you can typically expect an equivalent of 10% of the maximum power continuously over a 24hr period)! So a hybrid of both solar and wind would supply all of the domestic needs.
  Here is a little calculator to help:

  Enter the applience power (watts)
  Enter battery voltage (volts)
  Current supplied by batteries(Amps)




Batteries
Batteries can be the second most expensive part of the system. A good set of batteries will typically last between 3 and 15 years, depending on how deep they are cycled. There are also different types of battery chemistry, lead-acid, Nickle-Metal-Hydride, Absorbed Glass Matt and Cadnium. The reality is still that the lead-acid is the most favoured, it is a well matured technology and the cheapest available. My personal prefference would be flooded 2v lead acid batteries, which can be stacked up to make 12v. These are high capacity and are designed for industrial use.
The four points that make a battery unique are:

• Maximum Instantaneous Current Discharge
  (the rate in which the battery can provide instantaneous current)
  
• Current Leakage.
  (older batteries didn't hold their charge very well, but the better the battery, then the lower the residual charge leakage)
  
• Depth of dischage.
  (the depth of which the battery can be discharged without permanently damaging it)
  
• Number of deep cycle discharges
  (The number of times the battery can be discharged deeply before degregation to the battery chemistry)
  

If for example a battery is discharged to eg 25%-40% of its rated power regularly, it may have a good lifetime of say 4-7 years. Alternatively if a battery is discharged to eg 5% of its rated power regularly, it may have a life time of typically 15+ years. Therefore, if you choose only a 5% cycle depth, then it requires alot more batteries to be equivalent to a fewer batteries with deep cycle depth, and hence therefore a greater cost.
Good places to try to get hold of old batteries are train dept's, buses, milk floats etc. Ask if there are any old batteries they don't want, as usually their old batteries are alot better than new cheap batteries!
Note that all batteries should be kept in a dry safe environment, without the risk of any metal conductors falling across the terminals (remember DC is a hazard). They also need to be stored on a concrete floor, raised by a wooden plinth.

Make sure all connections with wires and terminals are correctly made. I have used crimp eyelets to ensure good conduction. Cable rating should be sufficient to carry the current required by the inverter. If using big inverters, you could use car starter motor wire.


Wind Turbines
The Swift wind generator is specifically designed for turbalent wind flow (which it is around a house rooftop).

My Installation - Technical Details

Here is the picture of my installation in my shed. At the moment it is still in early stages, (conduit is required around the wires). On the left are the solar battery chargers, in the middle is the consumer unit which contains all the MCB's, RCD's and disconnects. On the right is the inverter. All this is mounted on a wooden board mounted on the wall of the shed.

The solar pannels are mounted on an aluminion rack (brought from uni-rack). This is fixed to a metal post i brought from a metal fabrication company (they also weather treated it). The post is set into a 1m by 0.25m lump of solid concrete for strength (must be able to withstand up to 90mph winds). Note: I looked into a solar tracker, but i found an artical that suggested that the only time when solar trackers become effective is for the first 2 hours and the last 2 hours of the day, but as we live in the northern hemisphere, i think the effects of the tracker would be marginal compared with standard fixed array rack (ie cost vs effectiveness)
The solar pannels are wired up with bypass diodes and into 2.5mm square 3-core cable, with dc +ve, dc -ve and earth. These are then fed into the shed. The wires come directly into the solar chargers. The output of the solar chargers feed through a 16Amp MCB through a battery disconnect (another words a two pole switch) and into the batteries. The batteries are wired in parrallel and at about 840Ah. The batteries also feed through a 20Amp MCB into an inverter. The output of the inverter (AJ201) feeds through a 100Amp RCD, 4Amp MCB and into the cables running to the house. There are also a couple of 4amp MCB for my shed utilities. The hope is that once i have a wind generator, i will upgrade the inverter to a 1.4kW Sinewave inverter, which will drive the main utilities in the house.
All the MCB's and RCD's are fixed onto a standard DIN mounting rail inside the consumer unit, with battery disconnect built in.


Here is a list of costs to give you some idea of how much things are to buy if you decide to install yourself.


Items	Cost (pounds sterling)
solar pannels (kyrocera kc125w)	2 x £400
inverter aj201 (12v dc to 240v ac 50hz true sine)	£170
chargers (steca solsum 8.0x)	£25
solar pannel array (uni-rack)	£80
solar pannel array post	£65
batteries (bank of 35ah sealed lead-acid)	free - given to me
consumer unit (8 way + double pole switch)	£35
cable	£50
connectors	£10
MCB's	£50




List of Interesting Documents which may be helpful:
Solar Charger I'm using (Steca Solsum 8.0x)
Inverter i'm using (AJ201)
Solar array frame (Uni-Rack)
Article on Uninterruptable power supplies (by IEE)
Guide to PV system and design (California Energy Commission)
Calculating PV angles (Homepower)
KC120 installation guide (Kyrocera)
Data sheet for the Kyrocera KC120
Battery Life Cycle (Sandia Lab)


List of Interesting Links:
12VoltZ
Adverc BM
Ampair
Appropriate Technology Library
Backwoods Home Power
Barden UK Ltd
CPPowerAutomation Power Products Page
Engenius_Home
Galeforce Wind Turbines (NI) Ltd.
Home Power Magazine
MORVEN ELECTRONICS
Rainbow Trading Post
Renewable energy from Dulas Ltd
SHORELINE
Steca
Studer AJ - SI Pure Sinewave Inverters
Sunpowered Energy Systems Ltd.
swift turbines
Useful Solar Power and Renewable Energy resources.
Wind and Sun Ltd
solar-wind