LOW ENERGY WALK
IN JESMOND
What:
A grid-tied photo-voltaic system consisting of:
- 8x 215W roof-mounted panels (giving 1.72kW possible),
- inverter to convert DC from panels to mains AC with remote display,
- generation meter,
- replacement import+export meter
When:
Ordered September 2009,
installed in 3 days, commissioned 6.November
Cost:
£11,233 gross, £8,733 after maximum rebate from Energy Savings Trust.
Reasons:
Several reasons:
- A fit of pique at banks for poor interest on savings!
- The calculation that it should reduce electricity usage by about 1/3 and thereby lower my overall green-house gas generation.
- The calculation that a system would reduce electricity bills
at current prices v.slightly more than the interest the money was earning.
- The belief that I'd be better off with something more tangible for my savings than numbers in a bank computer.
Benefits:
In the first 6 months of
operation:
- Generated 654 kWh of which we exported 350 kWh (53%)
- Imported 1,228 kWh so with the 304kWh generated and not exported,
my total usage was 1,532 kWh
- Generated 42% of my total usage.
Generated and used nearly 20% of my total usage.
- Electricity bill reduced by 304kWh ( 654 produced - 350
exported, about £42) So I've not reduced by as much interest
forgone because of the amount exported.
After 1 year of panel operation:
- Generated 1367kWh according to the inverter, 1267kWh according to the
generation meter.
After 1 year with the export meter:
- Generated 1245.6 kWh of which we exported 652 kWh (52%)
- Imported 2587 kWh, so with 593.6 kWh generated and not exported, my total
usage for 2010 was 3,180.6 kWh
- Generated 39% of my total usage.
Generated and used over 18% of my total usage.
- Received and signed (at last!) the Feed in Tarrif contract that should
pay 41.3p/kWh generated with an extra 3p/kWh exported for 25 years from
2010-04-01. The first 9 months of the contract returned
£454 in addition to the £90 or so saved by the 593.6 kWh of
locally generated power we didn't have to import. This represents a much better
return than my building society's savings rate.
The system should just continue generating electricity whenever the
sun shines.
The panels are guaranteed to maintain at least 80% of rated output for 20 years.
Disadvantages:
- Only generating during the day and needs sunlight to work well.
- Grid-tied means that if the grid power goes away,
the system shuts down to protect anyone
working on the grid. I considered a stand-alone system but it would
have been more expensive, needed more internal rewiring to make
use of the power and required maintenance of batteries with a
limited lifetime.
- It doesn't help the
main use of energy in the house: heating during the colder months.
Lifestyle Changes:
- We try to use generated power to avoid importing where possible:
- We do laundry and dish-washing during the day instead of overnight.
- We use a 900W travel kettle for small amounts of water.
- I've tried using a portable induction hob for some cooking because its power can be kept low enough to avoid importing power.
- I take a lot more
care about turning off computers & etc. when not in use.
Other Changes:
- I use a 'clamp meter'
to measure total electricity usage in real-time: because of the
immediate feedback I find it good motivation to check it regularly and investigate unusual readings.
Preparation:
- I've been recording
meter readings for several years to give me a baseline to compare
any changes against. Since the end of 2008 I've been recording the
values at http://www.imeasure.org.uk/
- Before installation,
I used plug-in power meters to measure every plugged device in the
house and replaced or stopped using the worst offenders.
- I installed
switchable multi-blocks to make it easier to turn off groups of
equipment (e.g. computer+screen+printer, hi-fi, bedside
clock+chargers).
Aims:
- Try to replace more imported power with locally generated.
- Work on insulating the areas with highest heat loss: the ground floor
then the back walls.
- Think about a Solar Hot Water system for domestic hot water and/or
(partial) heating.
Notes:
