FAQ's

Solar panels that generate electricity are called Photovoltaic or PV panels. There are a few different types of panel available. The main 3 types are Monocrystalline, Polycrystalline and Amorphus. They all have their advantages and disadvantages.

Monocrystalline (single dark blue colour) has a typical efficency rating of about 15-17%. Costs are usually slghtly higher than other types due to complicated manufacturing techniques. 

Polycrystalline (lighter blue broken glass appearence) is similar to monocrystalline except the slices are made from multiple crystalls grown together. Costs are slightly lower and efficiency is around 12%. These panels suffer from efficency loss at high temperature.

Amorphous (brown gloss as seen on calculators) operates at around 6% but has the advantage of being flexible. Larger panels tend to be more expensive than crystalline versions as they are less popluar.

A rough average to work with, worst case and best case scenarios. In the UK testing with a range of panels, controllers and batteries has given us the following averages. As long as the panels are mounted south facing between a 15 - 70 degrees angle you will generate and store in to an off-grid system: 

0.05ah per watt of solar PV in 1 winter day

0.7ah per watt of solar PV in 1 summer day

These figures are the worst average results we achieved over 3 week periods in the summer and winter months. It is a good starting point to calcultate your requirements.

All our panels use high efficiency Grade A cells that work without direct sunlight. The irradiating light that penertrates through the clouds is enough to generate power. Winter days are shorter and darker than summer so there will be a lower average generation.

An On-Grid solar system is usually found in Houses or BUsiness premesis. It connects the power generated from the PV panels to the Mains Power and National Grid. It is possible to be paid for this energy you generat by your power supplier.

An Off-Grid solar system uses the power generated to charge a battery bank. The power stored can then be used to power devices in a house, shed or remote building. Thes systems can be as small or as large as you wish. From a light in a shed to a whole house. 

An On-Grid system consists of: Solar panels and mounting system, Grid tie inverter, wire / cabling, safety breakers, and monitor.

What is required for an Off-Grid system?

An Off-Grid system consists of: Solar panels and mounting system, charge controller and battery bank. Options include: AC Inverter, DC breaker (dependent on PV size). With off-grid systems it is always recommended to use the most efficent appliances and devices to save on panel size. Panels and watts are usually more expensive than buying new high effiency devices.

Simply, a charge controller protects the battery and solar panels from damage. A charge controller takes the power from the solar panels and modifies it so that the battery is not damaged. A 12v solar panel can produce upto 21v at times, this can damage the battery and any circuits that run off the battery. The controller makes the charging voltage and current safe for the battery and circuits. When the battery is full the charge controller cuts off the charging to the battery to protect it from over charge and damage. This also extends the battery life. There are 2 main types of controller. The basic PWM (pulse width modulation) and MPPT (maximum power point tracking). PWM is more efficient than the very simple ON-OFF chargers that are outdated and we do not sell. PWM maintains the best from the batteries and is a stong, effective method. MPPT controllers are far more expensive but also they controll the panels output power with advanced technology and algorythems. These MPPT controllers are up to 25% more efficient than PWM.

The inverter is an electronic device that changes DC (direct current) in to AC (alternating current).AC power is comonly used in cars, vehicles and battery powered portable devices like television remote controls etc. AC is the power type that comes from your household power socket. DC to AC inverters are inefficient and waste up to 30% of the power you generate. It is almost always better to use high efficency 12vdc devices where ever possible.

For an On-Grid system it is down to budget and space available. 

Off-grid, firstly you need to calculate the amount of power you will require. This is done by finding the watt rating of all the devices you intend to run. Then times this value of each device by the time you intend on running it for. This will give you a total watts draw value. 

eg. You have a shed light that you wish to run on solar. The bulb uses 11w. You wish to use it for 20 hours a week. 

11 x 20 = 220w

To make this value into the amount of power you will draw from the battery you divide by 12 (since the battery is 12v)

220 / 12 = 18.33 round up = 19

You then need to take into acount when you plan to use it. If it is all year round then you need to make the calculation based on the winter value of 0.05ah /w/day. If only during the summer then 0.7ah/w/day. Times the necessary value by 7 to account for the full 7 days of the week.

For only summer use:

0.7 x 7 = 4.9 ah / w / week

Then take the AH figure you require for the weeks power. ie 19ah and divide this by the generation value. ie 4.9

19 / 4.9 = 3.87watts PV required

Winter use:

0.05 x 7 = 0.35 ah / w / week

19 / 0.35 = 54.3 watts PV required 

As you can see there is a fair difference between winter and summer values in the UK. Please be sure to take this into account when calculating. Please contact us by email info@sunstore.co.uk or on 0845 1800 654 if you are unsure or wish to discuss your project further.

In the UK panels are most efficent when facing south at a 40 inclanation.