WARNING are you Over Egging the Renewable Pudding...
January 9, 2015
As planning and CSR agendas just keep setting the bar higher it would seem that a mix of low and zero carbon technologies are set to become the future of energy requirements in buildings.
I so often see what I call "kitchen sink" specifications, "we'll have solar PV & thermal, CHP, Biomass and a gas boiler in case the whole thing doesn't work." Since we are amongst friends I'll tell you what I think of this approach: expensive, unreliable and who came up with that idea and how much were they paid!
Only truly integrated systems really deliver value and sensible returns on investment. It's almost stating the obvious but it's true and set to become even more important as the low and zero carbon energy generation market continues to move from early adopter to mainstream.
So what does this mean in practical terms? For me it's simple, start with the building or estate energy needs (without lot's of nesting contingencies!) and actually look at them. No don't stick them in a spreadsheet which churns out "the answer"; actually graph them and look at them. With a bit of experience they tell you all you need to know about the best mix to do the job and in many cases one answer jumps right out at you.
It's worth keeping an open mind for as long as possible so I always try to get to the next step with at least two candidates / technologies. In each case there will be system modes of operation where the technologies will complement each other and other modes where they will conflict. You might want to generate more electricity from your CHP but you don't have any heating loads and your ground loop is hot so you can't do any inter seasonal storage without impacting cooling efficiency. Try something else.
Next do some sums, nothing fancy just simple efficiencies and how much the most likely solutions are going to cost to install and in carbon and run cost terms (including grants and project finance if applicable). Out of this process you should get to the optimum system sizes for the individual technologies, a bit of trial and error generally sorts it out. Now along the way think practically, do you have space for the ground loop, is it installable or do you need an oil rig to drill the thing? Do you have plant space, is bio fuel available sustainably, will the control system be able to work out what's going on and act appropriately to avoid howlers like turning from heat pump heating to boiler never to return?
If you do this I bet you'll see some new solutions appearing. If you get stuck, call us and we can give you a steer. Our service is free at the point of entry.