off-grid blogs uk

Case study: off-grid self-building

We recently completed an off-grid solar PV and battery storage installation for an ongoing self-build project. This case study tells you a little bit about the customer, the project and the Solar Plants installation.

The customer

Bruce and Vanessa have wanted to complete a self-build project for over seven years. They had the ambition and dream to build their forever home; for them and their two children, 13 and 15 years old, to live in together.

Vanessa works at natural high safaris but said that the couple were about as green-minded as the average person. However, since installing solar PV, she has expressed how much joy it has brought and how progressive they feel, especially for their children.

The couple has recently moved into the home, even though the project is still ongoing. And once everything settles, they’re looking forward to learning more about how to control their energy consumption and show visiting friends and family.

The project

Over the years, they have had difficulty finding the perfect plot. Fortunately, in December 2016, the couple made the purchase of a modern, steel-frame barn through Class-Q permitted development. This legislation was introduced in 2014 by the UK Government, which allows the change of use of certain buildings from agriculture to residential use.

They instantly got in touch with their architect to begin planning the barn conversion. The property is 380 square metres and also has a beautiful external wood cladding. The property also has acres of land for the family to enjoy.

Unfortunately, a big issue was that the plot didn’t have a grid connection.

Image credit: (credit here)

The opportunity

In 2017, the planning for the project was finalised and construction work began. The couple also began the process of gaining a grid connection from their local district network operator (DNO) too.

Eventually, as construction continued, the couple had to begin negotiating wayleaves across neighbouring private land. The property was situated about 0.5 km from two different transformers; a three phase transformer to the east and a single phase transformer to the west.

Their DNO, Scottish and Southern Electricity Networks (SSEN), had quoted the couple a minimum of £28,000 for gaining a grid connection. This figure rose to over £35,000 once trenching and wayleaves costs had been taken into consideration. (Some of Solar Plants’ off-grid customers have been quoted over £100,000 to gain a grid connection).

The prohibitive costs combined with the difficulties to negotiate wayleaves, left the couple feeling less optimistic about gaining a grid connection. They began considering alternative options — solar PV being the main idea.

Due to the size of the property and the supply they were seeking from the grid, “numerous” people told the couple it wasn’t possible to power the building off-grid.

Hopes dashed, the couple visited the National Self-Build and Renovation Centre (NSBRC) in April 2019. The couple were hoping to find any company that could help.

Upon seeing the Solar Plants stand at the NSBRC, the couple scanned our barcode to register their details with us. Even though it was against all advice they had previously received, the couple wanted to make a final effort by at least inquiring.

Two months later, the family came back from holiday and entered what they still wished would be their forever home. When Vanessa turned the light switch on, she described it “as this incredible moment”. The home actually had power.

The solution

After visiting the NSBRC, our Head of Self-Build & Renovation, Gareth Bevan, got in touch with Vanessa about their project. After an initial chat, Gareth referred Vanessa to Ian Hewson, Solar Plants’ Off-Grid Engineer.

Ian began liaising with the couple’s heat engineers who were due to install two air source heat pumps at the property. The engineer explained to Ian that the property could be using 60/70 kWhrs a day during Winter — this helped provide Ian with an idea of what sized system the couple would require.

A site survey was arranged to be conducted at the beginning of May. Ian designed a ground-mounted installation for the couple that would be installed in a dip of the land near the property. By utilising the grounds, the building remained aesthetically unaffected and the solar panels were actually out of sight.

With the project still ongoing and plans which will cause energy consumption to increase (e.g. possibly adding an outdoor swimming pool), Ian designed the following set-up:

80 x 335-watt monocrystalline solar panels (28.6 kWh)
3 x 13.8 kWh BYD lithium-iron-phosphate batteries (41.4 kWh)
15 kVA Victron inverter charger (single-phase)
4 x 100 amp Victron charge controllers
Victron Octo GX control unit
20 kVA LPG generator
The entire installation, including VAT, cost around 20% more than gaining a grid connection. However, the couple will never have an energy bill to pay. Due to being a five-bedroom property, the savings will mean that by remaining off-grid was the cheaper option within just a couple of years.

The solar panels were installed using Renusol plastic trays, in four rows of 20. This means that technically the system is a temporary structure so the couple didn’t have to seek further planning permission.

Originally, Power Naturally were going to install two Mitsubishi air source heat pumps (26 kWh) but decided on an alternative. At the property, they now have a Daikin hybrid air source heat pump (8 kWh) combined with an LPG fuel tank. This works as an integrated system, whilst the solar panels provides both the property and heat pump power.

The batteries are designed to charge and discharge quickly from renewables, with an ability to handle large loads.

The charge controllers regulate how much energy from the solar panels goes to the batteries. This means that automatically the energy is being diverted from powering the property’s appliances, heat pump and the batteries.

The charge controllers also compensate for different temperatures; this improves the efficiency of the set-up. When the property’s swimming pool is complete, any excess energy can then be diverted to heating this for the family.

The installation was completed in a week. On one of the days, Vanessa’s neighbour’s son visited because he has a keen interest in renewables. Thomas joined Ian and the team, learning and assisting where able along the way.

In comparison, if they were able to gain a grid connection, it would have been a minimum of a four-month wait after submitting the application form. Vanessa was so impressed by how much of a quick turnaround Ian and the team were able to offer.

The cable between the solar panels and the other components is trenched underground. The rest of the technology is situated inside a plant room for easy access. However, everything can be controlled and monitored via a smart device app.

All of the electrics are ready so as the first fix and second fix of the project are completed, it’s a straightforward connection for the on-site electricians.

Many of our off-grid customers were originally in disbelief about what can be achieved off-grid. We’re passionate about providing people with their own green energy source. Whatever you would like to accomplish, let us know and see if we can help.

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