EvoEnergy was commissioned by Mr. Whitby to install an 8.2kWp ground mounted PV system consisting of 48 Sharp 170 NU Solar Panels. This system has a predicted output of around 6,800kWh/year of electricity.
This system was sized so that Mr. Whitby’s electrical demands could be met entirely by renewable energy. Any access electricity that is not used in his home is can be exported back to the grid.
Solar PV System Location
Mr. Whitby owns a large number of fields at the rear of his property and he decided to use some of this space for his solar PV system. As with any ground mounted system planning permission is required, therefore EvoEnergy recommended that the system be placed away from any public highway, so it wasn’t visible to others and will not alter the look of the landscape. The area of land chosen was a large open field with no trees or bushes and therefore no shade.
Solar PV Design
The area of land to be used was on a slight slope, meaning that the system framework had to be levelled. Up-stands were used so that when the Solar PV was installed it would be completely horizontal.
The frame had to be strong enough to withstand wind speeds in the area. In order to design a structurally sound frame wind calculations were undertaken to determine what needed to be done so that the system could cope in speeds up to 120mph. The frame was built into the ground using concrete slabs placed at equal distances apart. Theses slabs also acted as ballasts (weights designed to sit on the mounting frame).
There were two separate frames; each was designed to hold 24 panels. This is a large household system; therefore EvoEnergy recommended using Sharp polycrystalline silicon 170W panels because it is more economical to use more of the less efficient cheaper panels where there is no space limitation compared with using fewer of the expensive more efficient panels. The optimum orientation and tilt for PV panels in the UK is for them to be south facing at 30° to the horizontal. An advantage of using ground mounted solar PV systems rather than on-roof solar PV systems is that the system can be designed for the optimum conditions rather than having to work on a predetermined roof angle. Mr Whitby’s system was designed to face south with the panels tilted to 30°.
Solar PV Systems produce direct current (DC), this must be converted to alternating current (AC) to use in the home via an inverter. In order achieve the highest system outputs possible it is best to place the inverter close to the solar PV system. In this case an outdoor Fronius inverter was used.
The inverter was mounted a perforated metal sheet that was connected to the framework underneath the panels. This meant that the DC wire run was as short as possible, therefore losses were minimised.
Solar PV Installation
Firstly, aluminium mounting rails were placed horizontally along the length the frame work. Clamps that hold the panels in situ were then attached to the rails and the panels were lined up along the frame. Each panel was connected to the next using the electrical cables on the back of the panels.
These cables were then hidden from view and connected to the inverter.
The inverter had to be connected to the main distribution board in Mr Whitby’s house. A trench was neatly dug for the AC cable. Once the cable had been securely placed in the ground the trenched area was resealed and re-turfed.
So that the electrical generation from the solar PV system could be monitored an OFGEM approved meter was installed at the main distribution board.
At the inverter the 3 phase AC cable was passed through a main AC isolator, controlling the AC to both systems. The AC cable was then passed through a secondary AC isolator and connected to the inverter.
Finally the system was initialised and tested. After a few minutes harmonising with the grid the Fronius inverter sprang to life and was sending clean renewable energy throughout the house and back to the grid as needed.