No fossils in MY house...part 1 - heat pumps.

Wouldn't it be great if we could just take ourselves off the electricity and gas grids?  Provide our own sources of heat and electricity for running all our gadgets and household objects?  Some people have done it, but it's no easy undertaking for the majority of us.

I have looked at some options for our house.  We live in a city, in a reasonably large, but old house.  We have some flat roof space and we have a reasonably large garden (a bit over a hundred square metres.)  It should be possible to do something useful with that.

Given the garden, I was initially attracted to ground source heat pumps.  These are brilliant devices that work like fridges running in reverse.  They pump heat from the ground into your house using electricity to run the pump to move the refrigerant through a heat exchanger.  In hot weather it's possible to run them in reverse to cool the house down and heat the ground up again.  You simply bury a long length of pipe in your garden, fill it with "refrigerant" and install a heat exchanger.

The key parameter in a heat pump is something called the coefficient of performance - which is basically the ratio of how much energy you can extract from the ground divided by how much electrical power you need to put into the device to pump.  Numbers on the order of 4 or just under are good for a ground source heat pump.

There are however some challenges.  To get a good coefficient of performance one needs as small a temperature difference between the ground and the target as possible.  The ground temperature in the UK is about 11 degrees centigrade.  A target of about 40 degrees centigrade can be achieved at a fairly good coefficient of performance.  As you try to raise the temperature higher the coefficient of performance falls - and you also risk over cooling the ground unless you have a large enough capture area.

To get good use from such pumps therefore requires very good insulation and ideally switching from radiators to underfloor heating.  That pretty much blows away the idea for our house and indeed for anyone who isn't moving into a house built under the newest regulations for insulation.  We could just about rip up the floors to install underfloor heating - no easy undertaking - but the insulation problem is I'm afraid insurmountable.

There is a very useful site for anyone interested in such devices here.  I originally looked at the Iceenergy site - I am not endorsing their products - although plenty of high profile names are, including Claire Short, however it looks like a good place to start.  That said, they provide a product and some engineering, but you're expected to do quite a bit of the work towards an installation yourself.

If one doesn't have space for a ground source heat pump one could always go for an air source pump.  The principle is exactly the same - except the energy to heat the house comes from the outside air.  There are some obvious benefits since you don't need a garden to dig up.  Coefficients of performance as high as 6 can be achieved.  You still have the challenge of insulation to deal with - and you are more at the mercy of the outside temperature.  Whereas the ground temperature is fairly constant, air temperature varies - depending on where you live by perhaps a large amount.  The colder it is the higher the difference in temperature likely being desired and the less efficient the heat pump will be.

Of course, heat alone isn't enough - you need electricity to run the pumps.  More on that in a future blog...

Electric cars - the way to go

Cars are to me a very visible reminder of our incredible consumption of fossil fuels in the form of oil.  Of course, oil gets refined into different grades of which petroleum and diesel are just two.

When one stands over a motorway or observes traffic in a city, one can hardly fail to be struck by the sheer volume of cars and lorries and the amount of fuel they are burning their way through.  When they're stuck going nowhere because of congestion the fuel isn't even being used to move them - it's just heating the atmosphere.  The oil industry has gotten very efficient at distributing fuel - and cars have gotten good at going reasonably long distances between refills.  There are however an awful lot of cars out there.

There have been previous experiments in electric cars.  GM's impact car of 1990 was a very promising looking prototype.  There's a GM video on this site showing  the early vehicle - and it's very impressive.  Twenty years on and there are almost no electric vehicles on the road.  What happened?  There's a film, made in 2006, called "Who Killed the Electric Car?".  You can watch a trailer here.  Being a little wary of any films that have a political axe to grind in terms of their balance (particularly eco films), it still seems incredible that GM killed off their electric vehicles in 1999.  As a result I have little sympathy for the problems they now find themselves in as a result of the credit crunch.  (Now I'm getting political :-)).

Sinclair's C5 was rather less successful - a good idea but not well enough executed.  Sinclair did however show vision, as he had done before with watches, calculators and personal computers.

It seems that the time is right for a resurgence in electric vehicles.  Gordon Brown, the British Prime Minister recently announced just before the April 2009 budget that the UK would move to electric vehicles - although I haven't seen much follow up on this yet.

There are plenty of well documented challenges with moving to electric vehicles.  Battery technology being one, support infrastructure for recharging being another.  If you are unfortunate enough to run out of fuel in a combustion engined car then it is usually possible to carry a gallon or two of fuel from a fuel station to the stranded vehicle.  If you run out of electric power then your options are rather more limited - perhaps a solar cell on the roof would eventually give you enough charge to move again - that could require many hours of daylight - so don't run out in the dark!

Just plugging in to recharge may be ok for people who use their car for commuting relatively short distances or nipping to the shops - but it isn't likely to work for people travelling longer distances or who live in remote rural areas.

I saw a video somewhere (if I can find it again I'll post a link) showing a conceptual battery replacement  station where the car drives in and the battery is replaced automatically in about 2 or 3 minutes.  No longer than it takes to fill a car at a pump today.  How many such stations would be needed across the UK?  How far apart could they be?  How do you ensure that there are enough replacement batteries available at any one station?  How do you ensure enough standardisation of batteries to ensure compatibility?  How do you maintain the quality of the batteries?  How long would they take to recharge?  How would you pay?  Who would own the stations?  What do you do with the batteries at the end of their life?  There are a lot of practical questions to be answered here.  Whatever the answers there needs to be a practical business model.

It has been pointed out that electric vehicles are charged with electricity from the grid which is generated from fossil fuels.  This is of course true (although nuclear and renewables will contribute more in the future), but the power stations are far more efficient at burning those fossil fuels than vehicles - perhaps 75% more efficient.

Today the electric cars available for purchase are either very expensive (e.g. the Tesla) and/or of very limited range - suitable for urban use perhaps, but little else.  That's not to say they shouldn't be used - they may well suit a very large percentage of the populations' primary vehicle use pattern - but they are not a complete solution.

There are intermediate vehicles becoming available in the form of hybrids such as the Toyota Prius - but they are pretty expensive and effectively only increase the miles per gallon of fuel rather than offering a choice of electric or fuel power.  (According to the Toyota website, they can cover a mile at 31 mph on electric power only - not even enough for the school run.)

All that said, it seems to me that electric vehicles offer great promise, even if initially only in urban environments where the infrastructure to support them can be more easily deployed.

We just need to make sure that nobody kills the electric car again!

Light Bulbs and Oil Wells

There have been a couple of energy related happenings in the last few days.

EU legislation banning the sale of 100 watt incandescent light bulbs for domestic use came into force and BP announced a huge oil find in the Gulf of Mexico.

There has been much wailing and gnashing of teeth over the light bulb ban in the UK.  The complaints are over different aspects of the alternative energy saving bulbs - known as compact fluorescent lamps or CFL's.  These use about a quarter of the amount of energy for the same level of light output - in other words they are more efficient.  There are a few issues with them.  They put out a different spectrum of light compared to tungsten filament incandescent bulbs - which many people complain is colder than the light they're used to.  They also contain small amounts of mercury meaning that the disposal of the bulbs needs to be managed more carefully.  Finally they take time to warm up - perhaps as much as a minute before they're up to full intensity.

There are other complaints about the new bulbs - their life is severely reduced by short on-off cycles - it's recommended that they be left on for at least 15 minutes to overcome this effect.  Some people complain that they trigger health issues such as migraines.  Without doing proper trials - which would be very difficult to do in a true blind (sic) sense - it's impossible to verify such issues, so we are subject to anecdotal reporting.

How much energy can be saved by using these bulbs?  According to the article in the above link the European Commission estimate up to 40 Terawatt hours per year.  That sounds like a big number - we should do some sums to verify this.  Other estimates say up to 7% of domestic electricity.  It's important to get a like for like comparison - including the amount of energy used in the manufacture, use and disposal (recycling) of both types of bulb.  I haven't managed to find those numbers yet.  For the end consumer, if the bulbs last as long as they are advertised then there will be a net saving of a few pounds per light bulb.

As one respondent to the BBC pointed out, in terms of CO2 savings they can catch a jumbo jet to fly to the other side of the world (a return trip to the US in a fully loaded plane will generate about 2 tons of CO2 per person) but they can no longer buy an incandescent light bulb.  That doesn't make switching to low energy bulbs wrong - it simply isn't enough to address our current energy addiction.

The BP oil find is I think mixed news.  On the one hand, great - we can go on living our current lifestyle for longer.  On the other not so great - we will go on living our current lifestyle for longer.  This will do little to discourage our continuing consumption of a limited resource.

I hadn't appreciated that typically only 30% of the available oil in a well is extracted - I'd like to learn more about that. This is a deep well and I'd also be curious to know how the cost of extraction will compare with oil elsewhere in the world.

Our political ambivalence towards energy usage needs to be addressed.  If we are going to move away from fossil fuels before it's too late to avoid a major energy crisis I personally believe that legislation will be required.  For that legislation to be successful and supported by the populace we need to start addressing the problem in a considered manner.  That's a hard thing to do when large numbers of people from different walks of life around the world are involved.  The human race doesn't have a great record for widespread considered and sensible debate.  Self interest and emotion tend to dominate and facts get rapidly lost in the melee.

It's windy out there...but is it windy enough?

Much is being made of wind energy as a key renewable resource.  The question is whether or not there is enough of it to provide for our needs.  Wind is not a constant - even though it might seem like that sometimes!  In fact it varies hugely in most places from day to day and week to week.  It also varies a great deal from place to place.

David Mackay's estimates for onshore wind energy are an average of 2W/square metre across the UK.  To turn that into enough useful energy for the UK will require a lot of wind turbines.  With those numbers, even if we covered 10% of the UK land area with wind turbines (not very likely) we would generate only 20 kWh per day per person - a long way short of the 125 kWh per day average that we use today.  That might be enough to provide about half of our typical domestic needs.

As with waves, once wind has been used to do work by turning a turbine, it is slowed down and is not then able to be used again.

Wind farms are springing up in a number of places and lots of companies are busy building them, with plenty more to come.  How many windmills will we need?  Where can we put them?

There are plenty of impressive sounding 10 or even 100 mega-watt numbers being thrown around for individual wind farm output - but UK energy consumption is in the 10's of giga-watt range.  The other problem is that these tend to be peak numbers - you can only achieve that when the wind is blowing within a fairly narrow range of optimum speeds.

Wind energy captured by a turbine is proportional to the area of the blades multiplied by the cube of the wind speed.  (Cyclists know this relationship well - the wind resistance goes up cubically as you pedal harder.)

This cubic relationship is one of the things that makes wind farm design a bit tricky.  Too much wind and generators and transmission capacity can be overloaded and the turbine blades themselves could be damaged - so over a certain limit the turbines have to be shut down.  Too little and the turbines won't even turn.  A lot of work has gone into making wind turbines operate across wide ranges of wind speeds - feathering the blades for example - but it is still a challenge.  In many ways achieving a predictable output is more important from a practical perspective than achieving the highest possible output.

The industry and the press tend to talk about two sources of wind energy - offshore and onshore, which funnily enough are either in the sea or on land.    Mackay's book estimates an average 3 watts per square metre for offshore wind.  The main benefit is that the wind is steadier and more consistent and not affected by mountains and trees.  The engineering challenges of offshore wind farms are not insignificant, there's a cool marketing video on the RWE website showing the building of the North Hoyle offshore wind farm.  This farm will generate a peak of 60 MegaWatts of electricity.  Compare that with a typical coal fired power station generating on the order of 1 to 2 GigaWatts - 20 times as much in a much smaller area.

In summary, wind energy is useful - but on it's own it isn't going to be enough to get us off our fossil fuel habit.

Energy from the sea...

There are a couple of ways of getting energy from the sea - tidal energy, which is effectively energy from the moon, since tides are caused by the moon orbiting the earth - and wave energy, which is energy from the sun causing wind which whips up the waves.

The methods for extracting these two types of energy differs.  The big benefit of tidal energy is that it's predictable - and constant (in that the tides happen twice a day every day - well almost - although the height of the tide will vary depending on whether the sun and moon are aligned or in opposition or somewhere in between.)  I haven't seen much beyond the theory yet on extracting tidal energy - that may be due to my ignorance - but tidal barrages are likely to be big and thus nimbyism and other practical problems are likely to dominate.

Wave energy suffers from the same problems as wind energy in that if the wind drops, then the height of the waves will drop and there will be less energy available.  The converse is also true - if the waves get too big then the wave generator could generate too much power, causing electrical damage or be physically damaged.  Sea waves are hard to predict - quite a bit of work has been done making practical measurements and then creating mathematical models to allow engineering analysis to be done.  These go by names such as Pierson-Moskowitz and JONSWAP.  One of the interesting things for me is the similarity between this work and some of the more traditional signal processing that goes on in the telecomms world.

There are a few companies in Scotland working on wave energy.
[2017 update: Since I originally wrote this, the two Edinburgh companies mentioned below have both gone out of business.  You can find a history of Pelamis here at https://www.furnacecompare.com/energy-efficiency/pelamis.html - including stories of intrigue and espionage.]

Two in Edinburgh are Pelamis Wave Power (with their Pelamis device - 50 - 70 metre water depth) and Aquamarine Power (with their Oyster, nearshore 10 - 12 metre water depth.)  Another company based in Inverness is Wavegen who have built a prototype onshore wave generator on Islay.  These devices each have their own advantages and disadvantages.  They each have some interesting videos on their websites that are worth a watch.  Both Oyster and Pelamis have been deployed at the European Marine Energy Centre (EMEC) at Orkney.

It would be nice if you could simply line these devices up - Pelamis in the deep water, Oyster in the shallow water and the Wavegen device onshore, but unfortunately it doesn't work like that.  Decent size waves require a long "fetch" - and once the energy has been extracted by one of these devices that's it - you can't have the energy twice.

I happened to stop by Pelamis Wave Power this morning whilst out for a bike ride.  A couple of their big tubes were visible in the construction shed.  I wonder if these are the ones ordered by E.ON?

Smart Grids - The Evolution of the Electricity Network

In the 20th century UK electricity networks evolved from a group of regional islands to a national grid. In the UK there are today approximately 140 "big" power stations. Traditionally the flow of electricity is "downhill" from generator, through distribution to the end user. The grid that carries this flow is aging - at least 40 years old in most cases.

Such a network will not be sufficient for the future. Renewable energy sources will be more numerous and more distributed. As individuals install their own small renewable energy sources it will be advantageous to be able to connect them to the grid to provide additional power. In other words there will be a need to integrate a diverse set of generation capabilities.

A network built around renewables will probably be more susceptible to variations in weather (for example wind turbines have to be shut off in high winds to prevent damage and in low wind they will generate less power.)

A smarter system for managing the generation and distribution of electricity will be required if we are to take advantage of this distributed generation and if we want to ensure security of supply.

Smarter use of electricity is envisaged, with consumers being able to make use of cheaper off-peak electricity (much like off peak travel is typically cheaper on the railways.) This leads to the idea of a two way network that manages information related to the supply of electricity - in many ways not unlike the internet that so many of us use for communication and information today.

To this end moves are afoot in Europe and the US to develop the technology to build so called Smart Grids.

Within Europe the Smart Grids European Technology Platform - http://www.smartgrids.eu/ is a consortium of interested parties focused on developing the technology for such a network. There are a number of papers on this site describing the vision for Europe and the Strategic Research Agenda.

There is an American Department of Energy document available
http://www.oe.energy.gov/DocumentsandMedia/DOE_SG_Book_Single_Pages(1).pdf which describes smart grids at a fairly high level - I'd recommend this as an easy introduction to the subject.

There is also an interesting paper from the Global Environment Fund with a US focus on the need to modernise the supply and management of electricity http://www.smartgridnews.com/pdf/TheElectricityEconomy.pdf

These are all fairly long documents - but the vision is similar. The electricity supply industry is ripe for modernisation.

How much energy do I use?

I started reading my gas and electricity meters about a year ago. I used to read them regularly many years ago and fell out of the habit. It's useful if for no other reason than to know if the utility companies' estimates are even close.

I subsequently discovered through David MacKay's book, the readyourmeter.org website. The idea is that you can enter your meter readings on the website (ideally on a fairly regular basis) and keep track of your energy usage, CO2 emissions and so on for your household or business. It's not the greatest website - it would benefit from being a bit more intuitive in terms of how to draw the graphs for your selected building(s). It is however a good idea in principle.

The other thing that could be done is to convert gas readings into kWh to make easier comparison with electricity. One's gas bill usually explains how to do this. The calorific content of natural gas is not constant across the network and a correction factor needs to be applied, however this is not usually very significant.

Anyway, from the readings over the last 12 months it seems that as a family we used 7500 kWh of electricity and 47000 kWh of gas. Given we are a family of six, that's not too bad - but if there were only four of us I suspect it wouldn't be a whole lot less. It works out at about 25 kWh per day per person. That said the gas usage is pretty high. We use gas for hot water, heating and cooking. It turns out as one might expect that the majority is used during the winter months for heating. We have an old, inefficient boiler - although replacing it is quite an expensive option. We live in an old house and the opportunities for improving the insulation are very limited - no loft and no cavity walls. We have for the most part switched to energy saving light bulbs.

What about transport? We are a one car family - we traded down from two cars about 5 years ago, mainly on economic grounds - and I started cycling to work - or in the winter cycling to the station and taking the train. That's about 3000 cycling miles and 2000 train miles per year. We cover about 6000 miles per year in the car - well below the national average, but certainly more than we need to. I fill the tank approximately every three weeks. I haven't done the sums to figure out how many kWh that translates to yet. Watch this space. Family bus usage is pretty limited. As a family we typically take one return plane flight per year to Europe. In the past I used to travel by plane fairly regularly as part of my job, but in recent years that has fallen to approximately one intercontinental and perhaps one European return flight per year. Again I haven't yet done the sums, but I expect that the plane travel dwarfs all our other travel energy usage.

I really don't have a clue how much energy we use in terms of the amount of "stuff" we buy - it's probably quite significant.

Of course, knowing how much one uses is one thing. Reducing it is another.