Friday, 22 September 2017

Why I haven't installed a heat pump (yet)

If you read this blog you will know I am keen to promote heat pumps as a low carbon heating technology, so I feel a bit of a hypocrite not having one at home. Since we have insulated our house as much as we can it is a logical next step to a low carbon house. So I made enquiries with two heat pump installers - but no joy. This blog post is a personal story. Every house is different and doubtless you won't meet exactly the same issues, perhaps even none of them.

Friday, 15 September 2017

The cost of building too many solar farms

Solar panels give us plenty of power in the summer when we don’t need so much and not much in the winter when we do. Building solar is like going to the shops to buy a winter woolly and buying a stack of T-shirts instead. Last time I wrote about this I focussed on our pattern of energy demand and how that can best be matched to wind and solar generation patterns. I concluded that we need some solar now but less in the future. That post was criticised for ignoring costs. So this time I will discuss the extra costs of investing in the wrong sort of renewables.

Monday, 28 August 2017

How much water do power stations use?

It is world water week and the power generation sector is often blamed for high water consumption - how high is it really? First the headline figures. Current water consumption by UK power stations comes to around 13 l/person/day [1][2]. That is less than a tenth of the amount we use at home [3].

However, the amount of water used depends on the technology. Wind and solar power generation need no water at all but most nuclear and conventional power stations use water for cooling. Coal power stations use more water than gas, partly because they use water for cleaning sulphur out of the flue gases as well as for cooling. Nuclear power plants also use more cooling water than gas. This is partly because they are less efficient so they have to dump more heat and also because they don't generate any hot flue gases, so all their heat has to be dumped through the water cooling system.

Friday, 4 August 2017

Drawdown - review

My beloved has given me a copy of 'Drawdown - the most comprehensive plan ever proposed to reverse global warming, edited by Paul Hawken'. It is a superb book in many ways - incredibly ambitious and a real eye opener.

The book ranks 80 wide ranging strategies in terms of potential carbon savings, with estimates for up front costs and overall financial savings to 2050. Strategies range from wind power to vegetarian diets, from district heating to educating girls. There were some in the agriculture section I had never heard of such as silvipasture (growing trees and grass together for animals and tree products) and improved rice cultivation (a combination of improved planting schemes and intermittent drainage).

Some of the rankings are surprising - but on a closer inspection this is often due to their method of accounting, whereby only carbon savings over the business as usual scenario are included. This increases ranking for strategies that are not currently widespread, which is a good way to bring them to our attention.

Friday, 28 July 2017

What does a sustainable energy system for 2050 look like?

The National Grid recently published their annual 'Future Energy Scenarios' report which describes alternative futures for electricity and gas supply and demand to 2050. There are four scenarios of which only one satisfies our carbon commitments but I am struck by how similar they are in terms of electricity generation - where they differ greatly is in gas demand and use of smart technologies to manage infrastructure - including smart meters and time of use pricing.

Friday, 14 July 2017

One year on from the inverter upgrade

We installed our PV panels in 2011 and last year we upgraded the inverter system, installing SolarEdge equipment. We were promised better yields, but are we getting them? After one full year with the new inverter I have a reasonable answer. In this post I show how I have estimated the improvement, correlating yield with the old system with weather data from the MET office and using this to predict what we would have got recently if we had not upgraded. The prediction function I derived was 98% accurate, which I was very pleased with. Using this I have estimated the improvement to be 5.9%.

Tuesday, 11 July 2017

How much water is it OK to waste?

All water companies waste water through not fixing leaking pipes. This is OK up to a point. There is something called a 'sustainable economic level of leakage' which is the level where the cost of fixing leaks and the cost of not fixing them balances out, taking into account environmental costs. Obviously environmental costs are hard to put a finger on. So what is acceptable?