Although solar electricity seems a glamorous way to do your bit for the environment and save money,
probably far more effective on both counts is simply to reduce use and waste.
Every kWh of electricity saved avoids production of ~0.43kg of CO2.
Every kWh of gas (burnt on-site for heat) saved avoids production of ~0.19kg of CO2.
To that end I bought a
PM230 kWh meter
meter to accurately work out what power a device is consuming,
even when apparently off (eg the dreaded "standby" or "vampire" consumption).
I have measured the power used by some gadgets around the house and in my study,
to see what is worth turning off or even replacing, given that some is old.
Having done this survey (June 2007), we're going to make more effort to turn
things such as the PC and cable TV box and stereo off completely,
but the biggest potential saving is to replace my aging servers with one
low-power laptop (still providing essentially the same services) for less
than 5% of the electricity. At some point the laptop might even be moved
'off-grid' to solar power, but that's a separate consideration.
The laptop should pay for itself in one year in reduced electricity bills.
Thanks very much to Adam of XePhi
for suggesting and devising configurations and power-saving tweaks,
measuring power draw of his stock kit, etc!
I'm also replacing the last few old-style incandescent (filament) bulbs
with modern CFLs for about one 5th the power consumption. In particular,
the main living-room dimmer switch (which no one liked anyway) has been
replaced and the 3x60W bulbs are being swapped out for CFLs.
Only the bathroom light and one exterior bulb won't be replaced with CFLs
since I'm concerned about condensation getting into the electronics and
damaging them or even risking a fire.
(Update Aug 2007: testing CFL in bathroom and watching carefully for problems;
no problems observed as of Jan 2008.)
Without giving up any creature comforts we should be able to reduce electricity
use at home near 5x, to maybe ~3kWh/day base load with maybe another 3kWh/day
for one wash and one dry with the washing machine and one dishwasher load
and other sundries each day, ie ~200kWh/month (£20/month);
probably somewhat higher in the winter when more time is spent indoors, etc.
I confirmed with our power company that our current load (as of June 2007) is
~30kWh/day.
As of late July 2007 the old server farm has been turned off and replaced with
a much lower-power solution saving ~640W+.
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In late August 2007 our quarterly electricity bill arrived with a huge 30% drop
even though most of the power savings had only been in place for about 1 month
before the meter reading! So almost all our electricity had been for powering
these servers, and I'm now getting almost all the features that I was before
for a tiny fraction of the energy and a lot less noise and heat in my office.
On 1st September, at home all day (though on my own as it happens),
less than 4kWh of mains electricity was used over a 24-hour period,
compared to ~33kWh/day average for the previous quarter last year,
thus nearly a 90% reduction in usage if this day proves anything like typical.
Also, 4kWh/day is just about do-able by solar PV in the UK in our local area
(there's a practical limit of about 4kWp of RE that the local electricity
distribution network (EDF) will allow to be attached to one phase in a small
domestic installation), and 4kWp should be able to generate 4kWh/day even
on almost the darkest London winter days, so we could, with a grid-tie,
be a net exporter overall, and on almost every single day too.
Now that I've stopped using expensive computing equipment as space heating,
it will be interesting to see if our gas usage/bill goes up any in winter
to compensate. Even if it does, it's still better in money and
CO2 terms to use mains gas (methane) to generate
heat on site than to use electricity. If the house is too cold after
this change then it will be worthwhile improving our insulation, not so before,
which will be another good thing!
(For the record, the August 2007 gas bill was ~£30 for 28 units (875kWh)
for the quarter, ie ~10kWh/day, which is for heating and cooking,
and is about 1/3rd the cost of electricity for those purposes.)
On average a London 4kWp solar PV system might generate an average of ~10kWh/day
(across the whole year) so we'd still be net overall consumers of energy
between gas and electricity, especially in winter.
From 1st October 2007 we have switched to the Ecotricity "New Energy Plus" tariff, so every single unit (kWh) we pull from the grid has been directly (or offset) generated by some mixture of wind/solar/hydro/wave "deep green" (mainly wind) for a 5% premium above our old rate from our current provider (EDF).
Since we have cut our power usage by 80%--90% then we can easily afford to pay the extra 5% on the reduced bill!
Interestingly, Ecotricity claims that 99% of their customers don't choose the
'Plus' tariff, so are presumably still very price sensitive, possibly overly so
since trimming waste by 5% is likely to be easy for most of them.
(As of 2007/09 we're using about 7.1kWh/day,
and as of 2007/10 very slightly under 7kWh/day,
which is somewhat higher than my target of 5kWh/day.
On a sample January 2008 day with only me at home but typical consumption from
running one load for the dishwasher and one for the washing machine,
I observed between 5kWh and 6kWh use for the day.
The BWEA figures suggest that ~13kWh/day (~390kWh/month) per household is typical for the UK (though government figures suggest ~9kWh/day), so we're pretty efficient already IMHO.)
As of 2008/03/03 when we replaced our old fridge/freezer with an A+ rated one,
I expect our gross consumption to fall to ~6kWh/day,
and with the solar PV installed the previous week
I expect our year-round net consumption to be ~5kWh/day,
ie my original target for the whole house.
On 2008/03/13 with the rest of my family away and almost no discretionary usage
other than my laptop and a few cups of tea, I achieved a (nearly) 0kWh day,
ie the import meter was reading the same kWh units at the end of the 24h
as at the start. In reality I used about 0.8kWh more than was PV-generated.
For a tiny bit of perspective,
just one major investment bank said that if all the computer monitors in its
London head office were switched off every evening as of October 2007
then the bank would save as much as 500,000kWh per year worth £35,000
and reduce its carbon footprint by 21,000 kg of CO2.
Total electricity use in the UK in 2006 was 382.5TWh, ie 382,500GWh,
of which ~37% was coal, 36% gas, 18% nuclear and 4% renewables
(see chapter 5 of the UK's 2007 Energy White Paper (EWP)).
The Indian government target is to make available 1kWh/day to each household.
Local Solar PV Generation
As of 2008/02/27 a grid-tie 1.29kWp solar PV system has come on-line,
due for billing 2008/04/02 now that it passed formal assessment.
This system should, on average throughout the year,
generate ~2kWh/day (>4kWh/day in summer, but <0.4kWh/day mid-winter),
and reduce imports by ~1kWh/day, ie remove the effect of the office consumption.
As of 2008/03, the system seems to be in balance with our baseload
(ie no big/discretionary appliances nor the fridge/freezer running)
with the import meter stationary at around 40W of PV generation, ie ~1kWh/day.
Future
To cut use/import of grid electricity (and CO2 production) further we intend to:
- Upgrade appliances (eg washing-machine, dishwasher, TV) to more energy-efficient models.
- Try to run appliances such as the washing machine when the solar PV system is generating power, eg in the afternoons in particular.
Off-site and 'Peak-Demand' Usage
I clearly don't just use energy in my home and study, but also in travel,
at my clients' offices, and in the various hosted servers that I use worldwide.
As of November 2007 I'm trying to trim the power consumption of my offsite
servers a little, for example minimising consumption of my London (UK) server
at the time of UK electricity peak load (1600--2000 GMT in the winter Oct--Mar),
which reduces strain on the grid (a tiny amount!)
and saves the CO2 from more carbon-intensive sources such as coal and diesel
in 'peaking' and other generators at this time.
For my Mumbai/Bombay (IN) Web server I'm deferring non-essential work 0700--2300 local time, in the spirit of the 2005/05/04 demand-curbing order of the Maharashtra Electricity Regulatory Commission.
For the Sydney (AU) server I'm treating 0700--2300 (local) as 'peak' time,
based on load graphs for nearby Victoria.
I've been unable to find a load curve for Beijing, so assuming peak use 0700--2300 local time.
For the Atlanta (Georgia, US) server, apparently summer (Apr--Sep) 2pm--10pm EDT is the peak load window, so I reduce my consumption then.
As of 2008/01/13 I have dropped my Singapore (SG) server,
and I hope to handle the same global traffic with less CO2/day in future,
but with similar low-latency response by keeping well-distributed mirrors,
given that most of them are lightly loaded.
In particular, I aim to ensure that the main (best-connected) mirrors
are never all in low-power mode at the same time.
Also, we avoid using the dishwasher and washing machine at home
during winter peak-demand hours (4--8pm) so as to reduce overall CO2 generation.
(Rather embarrassingly, after many years of using our dishwasher,
I had not paid any real attention to its 'quickwash' cycle until 2008/04,
which seems to save 30% of the energy over our habitual prewash+wash setting.
Time to make that change...)
Time-of-Day Metering Suggestion from South Africa to Curb Demand
As of January 2008 South Africa has been experiencing rolling blackouts
(load-shedding) given various constraints on generation and transmission.
It will likely be several years before this can be fixed.
One suggestion floating around is to put 'larger' (more than average) users
on time-of-day metering where they have to pay more for energy at peak demand
(and conversely may pay less at times of low demand).
I think that this is potentially an excellent suggestion,
with the possibility of gently coercing the wasteful, idle and anti-social,
while avoiding hurting the (energy) poor,
so I wrote to my MP and MEPs 2008/02/02
(with the first couple of acknowledgements early on the Monday 2008/02/04):
Re: Reducing CO2/GHG from electricity generation
[Might you suggest] implementing a
similar rule to that currently being touted in South Africa to help
economise on electricity usage and deal with their acute shortages and
load-shedding black-outs?
It is nice and simple, doesn't penalise the (energy) poor, and has
analogues from deliveries of other constrained resources such as water.
Simply that any user of electricity that exceeds 500kWh/month gets
time-of-day metering, which is not necessarily more expensive, but
rewards those users for avoiding times of peak demand. In effect it is
a far more dynamic alternative to schemes such as 'Economy 7'.
It will also tend to encourage more economy in winter when electricity
generation is likely to be more carbon intensive.
We have the technology for time-of-day metering already.
If you wish, you can read about my family's efficiency efforts which
have brought us to about 210kWh/month:
http://www.earth.org.uk/saving-electricity.html
A couple of the MEPs have responded that they will forward my suggestion
to the relevant European Commissioner.
Syed Kamall, Conservative MEP for London responded:
Your ideas are certainly very interesting and I will certainly put them to energy experts in the European Parliament and in London.
However, we should also note that the acute shortages and black-outs being experienced in South Africa are partly due to Eskom pricing energy so cheaply (for political reasons) that there was no incentive to encourage energy efficiency and conservation. Eskom's low tariffs have also driven away much needed potential local and foreign private investors.
Let's hope that Eskom and the South African government have learned the lessons and move towards more energy efficiency.
I agreed that while the causes/motivations aren't identical,
the solutions might be much more nearly so.
On 2008/04/12 I received a letter from the European Commission
c/o John Bowis OBE MEP (London) that notes that:
The reduction of electricity consumption through the use of TOD metering ...
is indeed one of a series of differentiated methods applicable to energy saving.
The implementation of innovative measures aimed at reducing the energy demand
of the houses (and hence CO2/GHG produced from electricity generation) without
penalizing comfort is one of the essential elements in energy management policy.
The projects on Eco-building and Concerto are examples in this field and more
information can be found in their respective websites:
[http://ec.europa.eu/energy/]
and
http://concertoplus.eu.
See the early 2008 proposed regulations and the Homeflex study from South Africa.
Interestingly, an informal on-line poll of usage per month,
in a blog read by a worldwide audience including the UK and US,
indicated as of 2008/02/04 that the modal monthly kWh is around 500 to 600,
which suggests that that would be a good target threshold to maximise effect.
It might be more politic to start with a much higher value and ratchet it down
to avoid bringing more than 25% to 50% of users into its net involuntarily
and suddenly (and expensively in terms of meter changeovers).
When the poll closed in March the results as follows suggested that
a ~500kWh/month threshold would still be plausible:
| How much electricity do you use each month? |
|---|
| Less than 300kWh | 18 |
|---|
| 300 to 600kWh | 26 |
|---|
| 600 to 900kWh | 18 |
|---|
| 900 to 1200kWh | 8 |
|---|
| 1200 to 1500kWh | 12 |
|---|
| 1500 to 1800kWh | 2 |
|---|
| More than 1800kWh | 11 |
|---|
From Net-Zero Electricity to Negative-Carbon
It has been pointed out to me that being net-zero for electricity year-round
and using the grid to 'store' excess until needed
(eg in summer for winter, and in the day for the night)
is not the same as being zero-carbon.
An excess unit of solar-PV-generated electricity exported in summer daytime
probably displaces efficient CCGT (gas) burn
which is the least carbon-intensive fossil-fuel generation mechanism/fuel,
but a unit imported when the sun is down, especially at winter peak demand,
will have used in part a more carbon-intensive generation method and fuel,
so zeroing the electricity use has not zeroed the carbon generation.
This is especially likely given the "Large Combustion Plants Directive"
(LCPD, 2001/80/EC, PDF on the Europa website)
in force from 2008/01/01, limiting the total number of running hours of
'opted-out' fossil-fuel generators to 20,000 across the 8 year period to 2015.
It is not clear how each plant will be run, but probably some will generate
only at times of peak prices/demand to maximise profit.
If we were completely off-grid then we'd have to cover each day's use
by our own RE generation, probably mainly from solar PV in urban London.
For our 7kWh/day to be covered in mid-winter we'd need 7kWp of solar PV
(plus a least a day's storage in batteries, or several days' for bad weather)
compared to the 4kWp we'd need for year-round net-zero electricity.
In fact, storage in batteries probably loses ~20%, so we'd better allow 8kWp,
ie double our net-zero-electricity value nameplate peak capacity.
And adding the storage to cover several days' bad weather redoubles costs,
bringing us to maybe £100k to lose/zero all grid dependence
and thus to erase the carbon footprint for our electricity.
However, we can then do better than zero-electricity and zero-carbon,
by reconnecting to the to the grid in summer to export any excess, maybe 80%.
We become a little solar PV generating station for the grid all bar mid-winter.
We might not even be allowed to export ~30kWh/day on our existing single-phase
connection, especially given that there is a current limit of ~16A peak.
However, if (for example) we optimised panel orientation for mid-winter output
and/or to spread generation throughout a summer day
(eg with panels facing east and west rather than all south)
possibly with some simple mechanical adjustments by season,
then our exports would reduce CO2 generation for other grid users,
and thus be 'negative carbon' from our point of view.
Our 8kWp system might produce ~4MWh/year excess to our needs, ie exportable,
(of maybe 6--7MWh/year available generated power total),
which we might sell in London to the local distribution network (EdF)
for ~£500/year including ROCs, etc.
So we wouldn't get rich that way (200 year payback cf 25 year equipment life),
but we would be 'negative carbon' for electricity.
This doesn't cover our space/water heating (CH/DHW) requirements.
It would be great to get overall energy efficiency to CSH (Code for Sustainable Homes) Code Level 4 or better as I understand it
(44% reduction in energy use over 2006 Part L building regulations, based on a gas-heated home, due to be manditory for new build by 2013 anyway),
though currently with ~10MWh/year electricity and gas consumption
vs an apparent UK average of 20+MWh/year,
we may in effect already be acheiving the implied energy savings in in practice.
(For example, we have the central heating thermostat at ~18°C during the day
and a couple of degrees lower overnight vs the
'standard' 21°C SAP (Standard Assessment Procedure) rating.)
As of late November 2007 I sent an enquiry to the National Grid to see if
a G83/1 (11kW/3-phase) inverter would be useful to them as part of their
standing/frequency reserve used to help maintain grid stability,
for example when a generator drops out unexpectedly or load spikes unexpectedly.
With a relatively small (6kWh) battery bank such a grid-tie inverter system
might be able to cut in very fast (within one cycle) and run for 30 minutes
in case of falling frequency or other stresses such as mid-winter peak demand,
even when the sun is down,
which seems to meet some of their technical requirements
(eg plant must be able to start delivery within 2 minutes of instruction,
have a run up or run down rate of 25MW per minute,
and must have capability to sustain output for at least 15 minutes)
but fails to meet another by more than three orders of magnitude
(that the plant can be instructed in blocks of at least 50MW).
I'm all in favour of explicitly contributing to grid stability as part of a
distributed generation system, and providing reserve might earn some fees.
ESCo
To deploy a really large solar thermal/PV system effectively in all regards,
including financially, it makes sense to have the capital and other expenditure
handled by an independent financial entity with, for example, VAT registration
to avoid 'losing' 17.5% down the cracks on expenditure, etc.
This company would be an ESCo (Energy Services Company), and there would have
to be a little care taken (and maybe some negotiation with the tax authorities)
to ensure that, for example, having a large chunk of the roof area covered with
collectors does not somehow undermine full capital gains tax relief on the
property. In particular, that is likely to mean the household paying the ESCo
at least a transparent commercial rate for energy provided. Presumably on
moving out the ESCo would have to be sold at fair commercial value to the new
home owners, but would that count towards stamp-duty thresholds for example?
As of early 2008 my consultancy company is going carbon neutral for the office at home
with a modest ~1kWp scheme, and will act as its own ESCo.
