Friday, 25 November 2022

Keeping warm in cold conditions - field studies of personal heating devices

My last post discussed how much we need to heat our homes to keep them healthy. The short answer was, about 8°C warmer than outside. This could mean temperatures as low as 12°C or even less. So how do we keep ourselves comfortable? Wearable devices, warm cushions, portable electric heaters? This post reviews some field studies described in academic literature. It seems to be a hot topic in China.

How warm should your house be to keep it healthy?

During the gas shortage some of us are turning our heating down to save money and some are turning it down to reduce demand and keep prices down generally. How low can we go? There is our own health to consider but fit adults wrapped up warm and with personal heating devices such as jackets and gloves can be comfortable in surprisingly chilly conditions (see the next post). What about the house? Central heating keeps the house dry as well as keeping us warm. How much heating do we need to keep the house safe?

Sunday, 23 October 2022

How to recycle solar panels: the cheap and cheerful approach

A recent journal paper suggests a new approach to recycling solar panels [1]. This is very much a cheap and cheerful approach (my words) compared to the gold standard ‘full recovery end of life’ approach. A comparison of the two methods is illuminating. The main author of the paper, Pablo Dias, has since set up a company called Solar Cycle to commercialise his process. It is great to hear of technology progressing from research in a university into the real world. Dias is from the School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, (Sidney, Australia) and some of the contributors to the paper were from other universities in Brazil but Solar Cycle has been set up in Texas, USA. 

The cheap and cheerful approach:

  • Involves only mechanical process and electrostatic separation; no high temperatures and no acids
  • Produces less pure products – more like metal ‘ore’ than refined metals 
  • Is less capital intensive
  • Can be economic at small scales

Wednesday, 12 October 2022

The effect of reducing radiator temperature on room temperature

Heating engineer experts have been complaining for years that condensing boilers were not being installed correctly to achieve the claimed efficiencies. A gas condensing boiler that is supposed to give you 92% could be giving you 85% or even less, if it has been set to heat the radiators at 70°C or hotter. Now that we have an energy crisis, this is one of the few things you can do to make significant savings for no cost and hardly any effort (if you have a combi boiler). Nesta have just launched a campaign on this. However the Heating Hub has been giving similar advice for some time. Some of the savings are from increasing boiler efficiency and some are from indirect effects on the room temperature. There is usually only a small reduction in average temperature but it will vary from one house to another. If you find you are uncomfortable you can tweak the thermostat up a bit to compensate.

Thursday, 15 September 2022

Can reducing the thermostat 1°C really save 10%?

It seems extraordinary that reducing the thermostat setting by just one degree can save more than 10% on your gas bill. A back of the envelope calculation suggests this has to be an exaggeration. However, when you take into account other sources of heat it can be an underestimate. Of course it depends on various factors and for a less well insulated house the relative saving is less, though the kWh and £ savings will be more.

Tuesday, 16 August 2022

Would water trading between regions reduce future costs?

Water supplies are under pressure again due to the very dry weather. So here are some facts about water usage: how much we use at home compared to businesses and industry, how this is expected to change, and how the cost of trading water between regions compares with new supply.

Thursday, 7 July 2022

Is using your home for energy storage really practical?

Electricity demand varies through the day, and the cost of supply depends largely on the demand peaks. Therefore reducing peak demand can bring cost savings. Most of us are going to be using electric heating in future, mostly with heat pumps, and this will be a major part of peak demand in cold weather. (Peak time currently is typically 4-7pm, including cooking time for many households.)

You can turn off your home heating for an hour or so, or at least turn it down for a bit. This could be useful to reduce demand during peaks or at other times when there is a short lull in renewable energy supply. The grid could be supplied from energy storage instead, but this is generally expensive whereas homes with masonry construction have ‘built in’ thermal storage. Turning off the heating you are using the fabric of your house as an energy storage system for free. (Well not quite free perhaps, you might need a controller like the Homely thermostat). However there are difficulties with this approach. On the whole, I do not believe it is sensible. The main reasons being:

When you turn the heating off in your house (or down) it gets colder. This means it has to be warmer than you need to start with, which means you are likely to have bigger bills overall.
Most homes cool quite quickly over the first hour or two. Preheating for an hour or two in advance does not help very much.
Some people are impervious to cold - many of us are not. Even quite small changes in temperature bring discomfort. 
Energy demand flexibility can be achieved more easily with other kinds of demand such as EV charging and especially with bi-directional vehicle to grid charging. It makes no difference to your wellbeing when your car is charged, as long as it is ready when you need it. 

In this post I explore (a) the rate at which homes cool, (b) how sensitive we are to cooling and (3) potential for demand response in buildings compared to EVs.