In Autumn of 2019, Atlantic Renewables designed, installed and commissioned an 85.7 kWp solar PV system with 306 panels and 9 inverters for an industrial business unit on an agricultural site near Crewe.
Overview of Project
The system needed to supply 9 different businesses, and include a battery system to assess whether including storage would produce a good return on investment.
The 9 businesses using the building each required a separate generation system. Their size and energy usage varied greatly, with some needing to power heavy machinery and others just using lighting, heating and small appliances. The separate supplies necessitated installation of separate cabling for each business to connect up the panels and inverters. The time of year and nature of the site meant that our installation team had to contend with damp, muddy ground during the installation. Having the skills, experience and enthusiasm to work safely and efficiently throughout helped us in completing the job in the required time.
After assessing how many panels could be fitted on the roof of the building, the next step was to look at the energy consumption of each business and how their usage varied over a typical day and a typical week. We then needed to compare this with the projected solar PV output we could allocate to that business. A projection for generation capacity can be made using the latitude, roof orientation and pitch, with a correction made for any shading of the roof. The comparison with energy usage, ideally over a year, helps to estimate the reduction in energy bills the system could provide for each business, predict whether a surplus would be generated at any time, and determine whether storage would be advisable.
The roof was mapped out to show the placing of panels, their connection into circuits to feed the power to an inverter efficiently, and which circuits would be allocated to which business units. We then looked at the total generation capacity for each business to assess the size of the inverter that would be needed for each unit. Some of the supplies were capable of generating more than 16A per phase. Jobs above this size require a G99 application for permission for grid connection before installation, while for smaller jobs notification can be submitted later by a certified installer. This is to ensure that the power infrastructure will not be damaged by carrying too much power. Managing Director Dean Flute worked with Scottish Power, who manage this area, to ensure the required permission was set up properly.
The design process also involved calculating wind loading and weight loading for the roof, to ensure that the structure would comfortably be able to withstand the forces involved.
The solar panels used were 306 280W polycrystalline panels manufactured by JA Solar. The 9 solar inverters for the main installation were all 3-phase Solis inverters, ranging in size from 5kW to 20kW. Each system was fitted with its own 3-phase generation meter.
Hybrid Battery System
The businesses in the industrial unit operate 9-5, and so their peak energy usage is well matched to the peak generation time of a PV system. Where this is not the case, it is cost-effective to install a battery system to store surplus energy generated so it can be used later rather than sending the surplus to the grid. The livery yard and stables has a relatively consistent power use of around 2 kW day or night, and was fitted with 22 solar panels giving a peak output of 6 kW in the daytime. For this reason, the customer was keen to have a battery system installed and evaluate this over a year to assess whether further storage capacity would be useful on-site.
Modelling the generation capacity and usage showed that there would be times when the battery was fully charged and the system was generating a surplus, so energy would be exported to the national grid. To ensure that for this particular system the current did not exceed 16A, we fitted a G100 export limitation device.
A storage battery for this type of situation needs to function well with a very different pattern of charging and discharging than a system used in an electric vehicle, where the battery will be fully charged and then nearly discharged before the next recharging. To be fully off-grid, the system and battery size needs to be sufficient to ensure that the battery does not discharge fully even when generation capacity is at its lowest. However, this would mean that for most of the year, the system would be generating a surplus that could not be stored and would be exported to the Grid. Due to a higher cost for the installed equipment and low revenue for exported energy, frequently generating a surplus would negatively impact the return on investment of the installation. A balance is needed to produce the greatest saving on the project.
Selecting the right battery type for the situation is also key to maximising the return on investment and ensuring reliable operation. A 6kW GivEnergy hybrid inverter and a fully recyclable lithium-ion battery were chosen. To use a storage system efficiently, a monitoring and control platform is needed. This is to monitor how much power is being generated and used, and how full the battery is in order to control whether surplus energy is used to charge the battery or exported to the Grid. GivEnergy offer a monitoring and control platform with full UK technical support.
The nature of the site meant exposing the system to dust and hair as well as changeable weather. The battery system and inverter were housed in a metal box to protect them. The performance of batteries in terms of the energy they can supply before requiring recharge can dramatically reduce in cold weather. For this reason we installed the battery next to the inverter, so that the heat generated as the inverter operates would keep the battery warm.
To enable wireless monitoring of the system, as the site did not have wifi available, we added 3G connection.
The installation process took 2 weeks on-site, with 7 staff involved. The site is a 90-minute drive from our main office, which meant some early mornings for Jason, Liam and Chris. Installing the mounting equipment for the panels took 2 days. All the fixing points for panels ran parallel for alignment of panels across separate units. 2 days were spent on installing the cabling, including laying an armoured underground cable. Installing the panels took 4 days.
Atlantic Renewables carry out all of our own installations, to ensure that work is completed safely, efficiently and in a professional manner. Our experienced staff are appropriately trained to comply with all the relevant safety standards and use appropriate PPE. We are an MCS Certified Installer, and all our installed systems are covered by a 10-year warranty. We are responsible for the whole process, from initial discussion with the customer through design and selection of the right components, to installation and commissioning. This means that all the relevant details are communicated effectively and the customer gets the right system for them designed and installed to a high standard, with nothing missed out.
Once installation had been completed, the necessary certification for the work was obtained. MCS certification verifies that the technology used for renewable energy generation has been selected and installed correctly, and will be maintained correctly. NAPIT certification for building and electrical work shows that the installation has been completed safely to required legal standards, and may be required for insurance purposes or when selling or renting out a property. Along with grid DNO notification, Atlantic Renewables provides MCS and NAPIT certification for all the solar PV installations we carry out.