Thursday, 16 September 2021

Turning down the radiators in unused rooms

To reduce our heating bills we are often advised to turn down radiators in rooms that we are not using. However, this can be a bad idea if you have a heat pump. The adjacent rooms leak heat into the colder room which means the working radiators have to work harder. This is generally OK with a boiler but not with a heat pump which gives better efficiency at low temperatures. With the radiators working harder they need to run hotter which often means you end up using more energy rather than less [1]. I have done some modelling to see what this effect looks like. The savings on the overall heating demand is probably smaller than you might think – typically 3.5-5.5%. On the other hand the impact on the radiator heat demand surprisingly high – 20% or more.

Tuesday, 7 September 2021

How much methane do oil and gas wells leak

Methane leakage matters – it is a relatively short lived but powerful greenhouse gas. Until recently, methane leakage has been hardly monitored and it is still not regulated. However, new techniques for monitoring are making it harder for energy companies to brush their emissions under the carpet.
Satellite data is increasingly used for tracking emissions
At current rates of global emissions (as far as we know), methane has a similar global heating impact to CO2, in the first few decades after release. [1]. The main sources from human activity are agriculture (especially cattle) and extraction of fossil fuels. There is also some methane released from landfill sites. However, it is really hard to be sure about these impacts, because emissions are not consistently measured. Recently we have developed techniques to measure methane in the atmosphere and track down where it is coming from. We have learned how to use satellite data for this and a new satellite is to be launched next year dedicated to this task [2]. In the interim we mainly use observations from boats or planes over small areas and coverage is sparse. 

Leakage from oil and gas wells vary by at least an order of magnitude
In this post I focus on emissions from oil and gas extraction. As yet there is no regulation on this, even in the EU. Emissions vary by at least an order of magnitude from one region to another and even one well to another. A considerable proportion of leakage is accidental which means it varies over time as well. The highest emissions are from fracked wells. 

Saturday, 21 August 2021

Comparing blue hydrogen with natural gas emissions

Hydrogen is in the news a lot lately, because of the publication of the UK government hydrogen strategy document. I was alarmed to find a recent article [1] saying that blue hydrogen (made from methane gas with carbon capture) is hardly better than grey hydrogen (made from methane without the carbon capture). The authors are Robert Howarth from Cornell University and Mark Jacobson from Stanford University). I have recently been saying that blue hydrogen is at best about a third the emissions from methane gas, which I think is bad enough - but this article suggests even that is naively optimistic. 

Obviously there are some vested interests trying to paint blue hydrogen as white as possible (pun intended). So I decided to dig deeper into the assumptions behind the analysis. There are three main sets of assumptions involved - about the upstream emissions, about the capture rates and about the source of energy used in the hydrogen conversion plant. Plus you can choose to use 100 year global warming potentials for methane or 20 year ones. Given the climate emergency, the 20 year timeframe seems more appropriate. Also I have chosen to compare blue hydrogen with natural gas, which is the fuel it would mostly replace. Depending on the assumptions you choose, you can make blue hydrogen decidedly worse or significantly better. I can only get it down to 1/3 the emissions of natural gas using the 100 year time frame, not over 20 years. 

Emissions from natural gas and blue hydrogen with the original assumptions in [1]. NG is natural gas, Blue is blue hydrogen, 100 years/20 years means using the 100/20 year global warming potential for methane 

Friday, 13 August 2021

Insights from studies of water shortages

Water shortages are increasingly common as an impact of climate change. Rainfall is not predictable, but most places have sufficient water reservoirs that shortages happen slowly and can be foreseen. At some point consumers are asked to be careful, and as disaster looms nearer these messages become increasingly frantic. Does this remind you of anything else? Climate change also happens slowly and not exactly predictably and exhortations to reduce emissions are becoming increasingly frantic.  Whether or not we will avert disaster remains to be seen. In this post I discuss insights from three journal article relating to damage limitation in drought. The first is about the near disaster in Cape Town during 2017/2018, from the view of the Cape Town water supply management. The second is also about Cape Town but from the view of residents – how the shortage affected different kinds of people. The third discusses how residents of Fortaleza (in Brazil) responded to increasing water prices during a drought. 

Wednesday, 4 August 2021

Fabric first is not the cheapest path – is it the best?

Greater Manchester has declared a climate emergency and set itself a target of delivering net zero housing stock by 2038. Now they have published a report detailing what is needed to get there. This shows that the fabric first approach is not necessarily the cheapest or even the fastest strategy to decarbonise houses in Manchester. However the authors still recommend it for a variety of reasons. They make some very good points, although there are going to have to be some trade-offs made in practice.

The report has been prepared by a consortium of very respectable consultants: Parity Projects, Energy Systems Catapult, ADE research and Bays Consulting. Their findings are in line with the results of work I have been involved in for BEIS (Cost Optimal Domestic Electrification - CODE) but frustratingly this is still not published - and nor is the government’s Heat and Buildings Strategy, probably delayed due to concerns over cost [2]. In any case, the Manchester report covers policy as well as costs.

The nub of the problem is illustrated by this one chart, representing an ‘average’ house. The height of the coloured bars shows carbon emissions, the yellow coins at the top show the capital costs and the black diamonds show annual energy bills.

Chart from the Manchester report [1]

Wednesday, 21 July 2021

Review: Housebuilder's Bible

Mark Brinkley's guide to building homes is a best seller and doesn't really need me to tell you how good it is. This is the 14th edition and he doesn't update it regularly only for love. However, he did ask me to check out some of the new content about low carbon heating. So I did, and while I was at it I looked at some other bits too, just because they are interesting. I can't say it is impossible to put down but it is certainly easy to keep turning the pages. I have never built or specified a house and probably never will, but if I did I would do well to start by reading this book. Actually I might want to build an extension one day and it would be useful for that. Also I have done a green retrofit (insulation) project and his section on that would have been helpful. 


Sunday, 11 July 2021

Do people with PV panels consume more electricity?

Calculations of the benefits of renewable energy usually make the assumption that people will continue to use electricity in the same way they did before. However, a lot of studies show this is not the case. Typically electricity use does increase by up up 20% of the renewable energy generated - a rebound effect of 20% However other studies find that on average electricity use is unchanged. A lot depends on financial incentives, and some on attitudes and some on the technology used. This suggests it is possible to 'nudge' this behaviour to gain the most benefit - how is the UK doing in this respect? It may be that we have, by good luck or judgement, avoided the worst outcomes.