As described on in chapter four, solar insolation or irradiance is a measurement of the amount of energy you can expect your solar panels to capture from the sun per square metre, depending on your location and tilt of the panels.
On page 36 there is a table of solar insolation values for London and in this appendix we have included similar charts for the rest of the UK. The values are shown as average irradiance measurements in kilowatt-hours, per square metre, spread over a day and averaged out
over a period of each month of the year.
We have already seen how the amount of energy captured from the sun varies depending on the tilt of the solar panels, time of year and location. The following tables show the results gained by mounting your solar panels horizontally and vertically, and gauge the optimum tilts for best winter and summer performance and, more importantly, best yearround performance.
Glossary Of Terms
AC - Alternating current.
Amorphous - A type of solar cell, also known as Thin Film, consisting of a thin film of non-crystalline silicon.
Anaerobic Digestion System - Gas produced by the breakdown of organic materials.
Angle - Also called Pitch and usually refers to the inclination of a roof in degrees.
Azimuth Angle Gauge - A device for making angular measurements in degrees with respect to true North.
Battery Bank - Batteries used for storing energy that are linked together to form a ‘bank’.
Combiner Box - An electrical enclosure allowing multiple panels to be combined in parallel and which also houses series string fuses or circuit breakers.
Controller - For an off-grid system using batteries, a controller regulates the amount of current the solar system feeds the batteries.
Crystalline - One of the two main technologies used for the production of solar panels.The other being non-crystalline amorphous.
Current - The flow of electrons in a circuit.
DC - Stands for Direct Current. A solar panel system generates low voltage Direct Current which has to be converted to AC.
Deemed - Estimated.
Efficiency - The extent to which a solar system can transform sunlight into electricity for domestic or commercial use.
Elevation Gauge - A device used in line-of-site surveys to reveal obstacles.
Energy - Power generated over a period of time. Electrical energy is usually shown as Watt-hours (Wh) or kilo Watt hours (kWh). 1 kWh = 1,000 Wh.
Export - Refers to the transference of excess electricity generated to the national grid.
FITs, Feed In Tariff scheme - A government backed scheme designed as an incentive to installing accredited solar systems.
Generation - The generation of all electricity via a solar system.
Green Deal - A government backed incentive for helping consumers finance energy efficient improvements to their homes without upfront costs.
Grid Connected - Also known as grid-tied and refers to a system that is tied to the national grid.This allows the home to run on solar electricity generated during the day with surplus energy being sold back to the energy company. In the evening and at night, power required by the home is imported from the grid in the usual way.
Grid-Tie - See Grid Connected.
Ground Fault Protector - Averts the risk of damage to the controller or solar array by immediately cutting off the flow of current, in the event of a short occurring.
Hydroelectricity - Electricity produced by water power.
Insolation - Also called Irradiance. Refers to the number of hours of sunlight and the strength of that sunlight at a particular location - taking into consideration the changes that occur throughout the course of the year.
Inverter - Converts the electricity from direct to alternating current suitable for use in the home.
Irradiance - See Insolation.
kWh - Kilo Watt hours. A measurement of electrical energy.
Latitude - The angular distance of a location in respect of the equator, expressed in degrees and minutes.
MCS - Microgeneration Certification Scheme. An internationally recognised, industry led and funded scheme focused on ensuringthe quality of renewable technology installations and products.
Micro-CHP - Micro Combined Heat and Power. A form of heating that produces electricity from the same source at the same time. Usually refers to mains gas or liquefied petroleum gas (LPG) butcan also be fuelled by oil or bio-fuels.
Monocrystalline - Solar cells cut from a single crystal of silicon.
Mounting System - The hardware used to fix the solar panels to the roof, a pole or the ground.
Multicrystalline - Also known as polycrystalline. These are solar cells cut from a block of silicon that has been made up of a largenumber of crystals.
New Build - A building that has yet to be occupied for the first time.
Obstacles - Any temporary or permanent fixtures that will cast shadowon, or block sunlight from, the solar panels at any time during the year.
Off-Grid - A solar system that is operating completely independent of the national grid.
On-Grid - See Grid Connected.
Orientation - Refers to the direction in which your roof is facing.
Photovoltaic - Often abbreviated to PV, photovoltaic simply refers to the process by which sunlight is converted into electricity.
Pitch - See Angle.
Polycrystalline - See Multicrystalline.
Power - A measurement of the rate of energy conversion in Watts (W).
PV - See Photovoltaic.
Retrofit - A term used when describing an installation on a building that is already occupied.
RHI - Renewable Heat Incentive. Another of the government’s schemes designed to provide financial backing as an incentive for people to switch from using fossil fuels for heating to renewable energy alternatives.
ROC - Renewables Obligation Certificate. A green certificate issued by Ofgem for eligible renewable electricity generated within the UK.
SAP - Standard Assessment Procedure. The government’s recommended procedure for calculating the energy rating of domestic properties.
Shade - See Obstacles.
Solar Array - A group of solar modules linked together.
Solar Cell - An electrical device designed to convert energy extracted from light into electricity by photovoltaic means.
Solar Modules - Also known as solar panels and consist of assemblies of cells designed to capture energy from sunlight.
Solar Panels - See Solar Modules.
Solar Shingles - PV cells that are designed to look like regular asphalt tiles while still being able to capture sunlight and convert it into energy.
Survey - In this book, ‘survey’ refers to inspecting your home to evaluate its suitability for a solar panel system and plan how toget the most from the government’s Feed In Tariff scheme.
Thin Film - See Amorphous.
Tilt - The angle at which the solar panels need to be mounted in order to get the best all year round performance, after taking into consideration the location’s irradiance values, roof pitch and orientation.
Voltage - Measured in Volts (V) and is the potential difference between two points, like the positive and negative ends of a battery. A measurement of the energy of electricity, in particular, per unit charge.
Warranty - Solar panels come with their own specific guarantees, and usually include a 5 or 10 year workmanship and materials warranty.
Wattage - An amount of electrical power expressed in Watts (W).
Wh - Watt-hour. A unit of energy equivalent to 3600 joules.
Wind Turbine - A device that can be free-standing or building-mounted and used to harness the power of the wind to generate electricity.
Wp - Watt-peak. The professed power of a solar cell or pa