Which Renewable Technology?

OK - so you want to install some renewable technology because you're worried about climate change or peak oil and gas and you want to do your bit.

So, which technology do you choose?

Well first let's suspend practicalities and assume that you have a nice south facing roof with no shading for solar photovoltaics or solar thermal and you also have space to fit an air source heat pump.

And we won't compare costs yet as we're waiting on details of the renewable heat incentive (RHI) which should be announced soon (March 2011 according to DECC).

Let's just think about how much energy, in terms of kilowatt hours (kWh), each technology is likely to provide for us in one year.

So, here are some (rough and ready) figures,

Solar Hot Water

The average domestic heating load in Scotland is 20,000 kWh/year. About 20% - 25% of this is used for hot water - and about half of your hot water demand can be met by a typical solar hot water system - say 2,500 kWh of heat.  

Photovoltaics

An average photovoltaic installation is between 2kWp and 3 kWp. 1 kWp generates about 850 kWh according to SolarCentury, so 3 kWp would generate 2,550 kWh of electricity.  

Ecocute Air Source Heat Pump (Seasonal CoP of 3.0)

The average domestic heating load in Scotland is 20,000 kWh/year. With a CoP of 3.0, the heat pump will produce 13,400 kWh of renewable heat from the air.

Conclusion

An Ecocute air source heat pump will produce over 5 times as much renewable energy as a typical photovoltaic or solar hot water installation.

 

And it gets you off rapidly depleting natural gas.

 

 

 

 

Which reneweable technology ? Submitted by mahall on 12 February 2011 - 9:49am.

Thanks for posting these figures Alister. I noted some points to comment on though.

First is that the Ecocute heat pump is still in the early stages of marketing and though it may be working well in those Scottish situations where it is installed, nevertheless it's a new thing to many people and we need to get more people seeing where one is installed and what the logistics and daily usage implications are before we will get lift-off in terms of installations. I expect the RHI will help too.

Second is that the location is key, in the sense that you won't at the moment get many ASHP's fitted in upper floor tenement flats whereas in individual houses, and possibly ground floors of tenements given the right level of insulation, it's more likely. Conversely solar hot water systems will be much more constrained and costly at the bottom of a tenement. Even at the top of a tenement, issues of roof responsibility will cloud the prospects of solar thermal for the present.

Third is that the interview with Dr Bakhtiari was in 2006. Although his general message is still valid, I think there have been some distractions and complicating elements in the detail since then - the effect of the financial crisis and recession, for instance. Also the recently better publicised issue of 'shale gas' or coalbed methane in various places, which seems to be making the fossil gas producers (and potentially the public) more optimistic about maintaining supplies, even if only in the relatively short term and with side effects that remain unclear.

To wrap up, I think we're getting better informed bit by bit as to what's appropriate in what context, but I don't think we're yet invariably getting better connected in practice when it comes to installation. I'm sure this will come though.

Mike

 

 

 

 

Air Source Heat Pumps and Tenement Flats Submitted by alister on 19 February 2011 - 3:54pm.

I agree tenements are tricky from the point of view of renewable energy installations.

But, if you lived in a block of eight tenement flats with two flats on each floor and the two ground floor properties installed air source heat pumps then, when viewed as a whole*, the tenement would be generating more renewable energy than if all flats had 3 kWp of solar PV installed on the roof or if all flats had solar hot water.

*Assuming each tenement flat had the average Scottish heating load.

 

 

 

 

Natural Gas Submitted by alister on 16 February 2011 - 12:02pm.

With regard to Dr Bakhtiari's comments in 2006 about world natural gas peaking at 100 - 105 TCF in 2008-09, and indeed Matthew Simmons' similar warning discussed in one of my previous blogs here, we are now in a position to look at the data.

Here is world natural gas production up to and including 2009 as published by BP.

World Natural Gas Production

 

We can see a peak in 2008 at just under 300 Billion cubic feet per day. Multiply this by 365 and we get just over 105 TCF annual production in 2008.

The decline in 2009 was 2.1%, the largest ever decline in natural gas production.

One data point doesn't make a trend, but so far, the warnings and the data agree.

We can drill down further into the data and get the next graph, again using data from BP.

World Natural Gas Production by Region

 

This shows the regions with natural gas production declines in 2009. These are -

• South and Central America (-3.2%)
• Europe and Eurasia (-10.2%)
• Africa (-4.6%)

Europe and Eurasia is the region with the largest natural gas production - greater than North America, and 32.5% of the world total in 2009. UK production was down 14.1% in 2009, Russian production down 12.1%. Norwegian production increased by 4.5%, but we have heard recently that Norwegian natural gas production will enter decline around 2015 as discussed here.