Off-grid solar electricity: a case study of a field studies centre
Posted by Cathy Debenham on 1 August 2011 at 12:37 pm
Solar generated electricity is the perfect answer for the Stafford Marsh field studies building on the Axe Estuary wetlands in East Devon. Off-grid, and a hard place to get electricity to, it was a "no brainer" according to nature reserve officer, Fraser Rush.
This is the first off-grid installation I've visited, and it was fascinating to see how it works. It's got two inverters. The first converts the DC (direct current) electricity generated on the roof to a battery-friendly voltage. The second inverter converts the electricity supplied by the batteries to mains (AC - alternating current) electricity.
There's a display (see second photo) that shows how much electricity is stored in the batteries, using a traffic light system. Amber gives a warning that's it low, and if it shows red it means turn it off now. The 1kWp solar PV panels were installed by Chris Rudge in February 2011, and so far the light has shown green continuously. However, there is a small generator to cope with the dark days of winter.
The key to the system's design is to maximise the life of the batteries - and so it won't allow anything to be used if it is above or below a safe voltage. A kettle would come in that category, so there's a small gas ring for making the tea. Other than that the solar PV system has coped with everything staff have thrown at it so far.
The field centre building is the nature reserve HQ, an interpretation centre for school groups and other visitors, and venue for events and bird ringing groups.
It's lit by LED work lights, there are pumps for the fish tank and water, a fridge and microscopes use electricity. Even extended use of a power point projector for teaching hasn't triggered an amber light. It also copes with overnight moth traps, and there's a barn own loft and bat loft wired up for CCTV, should they get occupants.
I found an off-grid installation like this much more exciting than a domestic, on-grid one. While both make a difference, this opens up such opportunities, and means you can avoid the disruption, huge expense and ugly power lines needed to get grid connected. It just makes so much sense.
Stafford Marsh Field studies building received funding from Making it Local.By Cathy Debenham
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