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What is Solar PV?

A 4 minute read

Solar PV - it’s almost as bad as a three letter acronym. What does it mean?

Solar energy is broadly split between solar thermal energy which uses the heat from the sun and typically makes things hot and solar light energy, which using solar panels actually generates electricity.

PV is short for Photovoltaic — photo = light, and voltaic  = electricity. We  simply call it PV. Photovoltaic (or PV) panels convert light into electrical current – commonly called direct current or DC.

We are pretty down on our weather in the UK but the good news is there still enough LIGHT even on a cloudy day to generate electricity from solar panels. Generation on a long sunny summers day in the UK is quite impressive, on grey but bright days at least some electricity is produced.  It will interest you to know that the number of rooftop solar installations in the UK is approaching 1 million.

Electricity (Load) - Watt?

The unit of measure for power is a Watt (W) – our kettle uses between 1500W and 2500W but a mobile phone charger only uses about 5W. When we add all the appliances that are plugged in and drawing power we call this the load, loads are often in the 1000’s of Watts so we commonly refer to Kilowatts (kW). An important consideration for  energy efficiency is to reduce your load by using energy saving appliances, timed/sensor switches and LED lights to name but a few.

Solar Panels

Solar PV panels started out on spacecraft in the 1960’s but are now affordable and efficient enough for use on the rooftops of houses and businesses.

Solar panels are rated according to how much power they can produce. The maximum power that a panel can produce at any second is called the Kilowatt Peak (kWp). In the UK you can install up to 4kWp (usually 16 panels) without special permission. A standard rooftop Solar PV panel has 60 cells and are roughly a meter wide and 1.65m tall and will produce 250Wp (0.25kWp).

Solar Panels are made of silicon, glass, aluminium and special plastics.

Solar PV Inverters

The electricity supplied by our grid and used in our homes is Alternating Current – or AC. Inverters use sophisticated electronics to convert DC current (from the Panels) into AC current that matches the frequency that the grid supplies and thus can be used seamlessly to run all our electrical devices, appliances and machines.

We’re all crazy about metrics – how much energy do solar panels produce. One metric calculates the number of kilowatts produced during the daylight ours and we get a unit called kilowatt hours – kWh. We measure both what we generate and what we use in kWh. This is what you get charged for on your utility bill – often referred to as a unit. An array (all the panels in the system) of solar panels can produce from a couple of kWh per day to several dozen kWh depending on the number of panels and the atmospheric conditions.

Battery Storage

It is now possible to store surplus energy in a home battery – for example at noon on a sunny day and then to defer use of that energy to a time when solar arrays are not producing energy. This increases the self-consumption proportion of the Solar PV electricity and reduces the exported amount of energy to the grid

Grid

In most of the UK, a standard Solar PV installation can generate enough electrical energy to cover the load for an average house for a year. Unfortunately, there is often a surplus on sunny summer days and a deficit on cloudy and rainy days and on short winter’s days. 

When in surplus, what you don’t use you share with others. Any surplus electricity gets fed back (exported) into the grid and can satisfy other demands. We commonly refer to the Solar electricity systems described here as grid-tied PV systems. In the UK it is assumed that a Solar PV system will export half of its generated energy to the grid, this energy is not measured but you get paid for the deemed amount - another bit of revenue.

The feed-in tariff (FIT)

Our government pays us for every unit of electricity we generate. NOTE: every unit! A generation meter is installed and every kWh you produce you get paid for – your energy company will send you a cheque or deduct the amount from your bill. If you use that unit of electricity and therefore don’t buy it from your utility company, you essentially get that electricity for free. Solar PV savings are calculated by adding the revenue received from generating electricity on the roof plus the deemed export tariff plus the electricity that you didn’t have to buy from the grid.


 

15 St. John's Street
Newport Pagnell
Bucks, MK16 8HE
United Kingdom

Telephone: 01908 915 565
Email: info@thegreenwaysolar.co.uk

Telephone: 01908 915 565
Email: info@thegreenwaysolar.co.uk