A new solar PV installation at a health centre can generate power right through the day following a decision to mount solar panels on East and West facing roofs to bolster those South-facing.
Marcham Road Family Health Centre in Abingdon, Oxfordshire, wanted the maximum number of panels possible for their new renewable energy installation, with NGRE recently fitting 77 on the practice’s roof.
However, while large portions of the complex roof face South, the building also has significant elevations facing West and East.
Utilising West and East Facing
In consultation with the practice, NGRE planned a scheme comprising of 8 panel arrays, three of which face South, one East and four West.
Greg Bishop, Managing Director of NGRE, said: “At the end of the day, your roof is what it is. Certain elevations face a particular direction, so it’s about getting the best out of what you’ve got. If all the panels were in a southerly orientation, you would get peak power at midday, but you might not want it all at that time.
“This design provides a good spread of orientations. With the addition of East and West orientations, when we consider the power generation graph, it’s quicker to come up in the morning and then the power generation continues later into the evening.”
He added: “The system is a good size for that building – a small commercial scale solar installation. We maxed out the number of panels for the roof space providing good peak power and extended performance throughout the day.”
Energy at the Beginning and End of the Day
Dr Timothy Robson, one of the partners at the practice, said: “Having a diversity of power generation and the power being more even through the day is proving really useful. We have energy at the beginning and end of the day. Even with the spread of directions, we generate far more power in the middle of the day than we are using and so if they were all pointing South we’d have massively more power in the midday than we needed.
“I’m quite glad the East and West facing panels are there.”
The System
The health centre’s system comprises 77, Hyundai 395w monocrystalline solar panels, producing 30.42kWp (an estimated achievable power of 24.26kWp), connected to a 25kW SolarEdge 3-phase inverter. Each panel is connected to an optimiser that allows the system to constantly track the performance of each panel, maximise the performance of the whole array and identify any problems quickly. Unlike with some systems, in which the whole array is affected if there is any debris or shading on an individual panel, the optimisers allow the remainder to operate to their full potential.
It is estimated that the system’s total annual power generation will be 19,380 kWh.
63% Reduction in Commercial Energy Spend Already
Dr Robson said: “It’s already saving us money. Since we’ve had the system, we’ve reduced our imported energy by nearly two thirds; 63%.
“I originally worked out that we could probably pay off the capital cost in 5 to 10 years and then it will save us a few thousand per year thereafter. Since I worked that out, energy has gone up so much more, so it might end up paying for itself sooner.”
Monitoring
The centre management will be able to monitor the system easily through an online portal or via the mySolarEdge mobile app. Using this they can keep track of their energy generation and energy usage either in real-time or historically using easy-to-follow charts, ensuring they use the energy produced as efficiently as possible. For example, users can compare consumption with production to see where, when, and how much of their free energy is being consumed and how much is being exported to the grid, allowing them to change to more efficient usage patterns.
The practice will be able also to use these figures to help them decide whether a battery storage system would be beneficial in the future
Future Battery Storage System – Almost Off-grid
Dr Robson said: “Battery storage is something we have definitely thought about but particularly since we’ve had the system, as we’ve discovered we’re exporting much more than we are importing.”
Since the system has been up and running, the centre has exported 1110kWh to the grid while it has imported 740kWh.
Dr Robson added: “At the moment we are paid between 6p and 15p per unit for the electricity we export whereas it costs us about 75p per unit to import. So it would be good for us to use that excess energy we export ourselves rather than buying it in and losing out.
“We are a daytime business really, but energy usage is still high even until 8pm, as we have cleaners in, so reducing imported energy at this time would definitely benefit us.”
Greg said: “The good thing about SolarEdge is that you can get empirical data about how the system is performing. In the future you can see if a battery storage system might be a good option.
“If you look at what they’ve imported and exported you can see that a battery would be very effective – they could almost go off-grid.”
Why Solar?
Dr Robson said: “It was a mix of reasons really. I’ve got some panels at home and I personally think we should be doing everything we can to reduce our carbon footprint and use less energy from the grid. So, it was partly investing in green technology and as a practice we also wanted to save money as we are a business.”
Why NGRE
Dr Robson said: “We got a number of quotes, but NGRE stood out. They were friendly, local and were reasonably priced. I was delighted that we were able to fit on so many panels so that in winter we can make the most of the sunlight available.”
Panel Orientation – Which Direction is Best?
The direction that a system’s panels face is one of the most important factors when planning a new PV system, as that will determine how much sunshine hits them throughout the day and therefore how much electricity they can generate.
The best direction for solar panels to face in the UK is Southasthe sun is always in the southern half of the sky in the northern hemisphere and facing South means the most direct sunlight exposure.
However, while South-facing panels will generate throughout most of the day, their peak power occurs when the direction of sunlight is perpendicular to the panels in the middle of the day, gradually rising to this peak power during the morning and tailing off through the afternoon and into the evening.
While the addition of East and West-facing panels will lessen the peak power generation of the entire system (as compared to them all being South-facing), more energy can be generated earlier and later in the day, so while the peak is not as high, the rise in generation is sooner and the fall off later.
And the difference in generation between South-facing and other orientations is not as much as you might think. According to figures from standards body, MCS, at 40 degrees roof angle, South-East and South-West panel orientation produces 95% of the energy produced by South-facing panels, while East and West orientation provide 80%.
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