Tuesday, 12 December 2017

Being together without travelling

Christmas is a time for being together, with family or with friends. But it is not a good time to travel, with bad weather often disrupting trains and planes and the roads clogged with extra traffic even when there hasn’t been an accident bringing progress to a standstill. Fortunately, there are other ways to contact family without actually being there, and they have come a long way from my childhood when there was only a phone with a huge handset and only one of us could talk at a time. These days:

  • You can put the phone to speaker mode, so groups can take part at either end.
  • You can wear a head set, and talk while moving around (exercising, cooking…)
  • You can use a phone with a camera (or a web cam) and have video as well as audio.
  • You can use a tele-presence robot which gives you freedom to move and look around at the other end.


Monday, 4 December 2017

The future of Transport

Will we have self driving cars or not? 'Travel in Britain in 2035' describes three plausible(ish) scenarios and only in one of them do self driving cars play a major role. They do make a big difference though. I heard about this report at 'The Future of Transport' organised by Cambridge Network. There were 6 presentations in total of which three involved driverless vehicles: one on self driving cars, one on self driving delivery drones and one on self driving mass transit vehicles. (Actually this was mostly about tunnels; the self driving bit was only incidental; driverless transit vehicles are common enough to be uninteresting, for example the London DLR). The other three presentations were the one on the future scenarios report, one on local transport plans (from the council) and last, but perhaps most interesting, one on local transport from the consumer side: Andy Williams from Astra Zenica discussing how their staff will get to and from work.

Friday, 24 November 2017

Energy performance for windows

A proportion of heat loss from our homes escapes through our windows - this is often quoted as 25% but it could be even more if the rest of the house is well insulated. How do you know when you buy a window that it is energy efficient? There is a rating scheme in common use, defined by the BFRC (British Fenestration Rating Council) and it combines several performance factors. Somewhere like the Green Building Store, that really cares about efficiency,  specifies each factor separately. You may not want the same kind of window everywhere, depending on the direction the window is facing and how much it is shaded.

The BFRC certificates look similar to EU energy certificates for TVs, fridges and such like, even though they are nothing to do with the EU.  The rating scheme (which goes up to A++) is based on a combination of three performance factors:
  • Conductive heat loss i.e. window U-value
  • Thermal transmittance, a measure of how much of the sun's heat energy will pass through as solar gain (this is different from transmittance of visible light).
  • Air tightness.

Unfortunately they do not publish the details of how these measures are combined to give a rating. (All the EU standards are described in detail on the Eur Lex website.)

Saturday, 4 November 2017

How is a thermal store different from a hot water tank?

People often ask if they can use heat from their solar panels for heating as well as hot water. The short answer is no, because the solar panels heat your hot water tank which supplies hot water to your taps, not your radiators. The long answer is you could, if you installed a thermal store instead of a hot water tank, though this may or may not be a good idea. A thermal store is also a big tank of water it works in a different way so it can be used for space heating as well as hot water. Thermal stores can be useful in various situations:
  • You can combine heat from different sources, e.g. solar panels or a wood stove as well as your boiler
  • You can store heat to optimise use of your heating system - for example if it is inefficient to turn on and off according to demand (particularly useful for log burners but also for other biomass boilers or even heat pumps).
  • It can store heat when power is cheap for use when it is expensive. For example, using a thermal store you can avoid running your heat pump at peak times and get a cheaper tariff (at least you will when we all have smart meters and time of use tariffs are available).
The size you need depends on what you want to do with it.

Wednesday, 25 October 2017

What will smart heating controls do for me?

People interact with their heating controls in different ways. Some people leave it how the engineer set it and dare not touch, others use the thermostat as an on-off switch; some want a set-up and forget system with only occasional need for twiddling, still others would really like something that is clairvoyant and does the best thing without them having to do anything at all. Most people agree that it isn't an easy subject. Can smart controls help? In fact what are smart controls?

Heating controls was the subject of half my Cosy Cambridge workshop on Monday. With the help of some friends we managed to cover all the basics and had a good discussion on whether 'smart' controls were a good idea, or rather under what circumstances you would benefit. You can download the slides from my website here.

Sunday, 22 October 2017

How much less water do modern houses use

Cambridge is growing and more people means more water consumption, which is a concern in this area. Will the new homes use as much water as existing ones? Building regulations require that new homes are fitted with water efficient appliances so that an 'average' person will use no more than 125 litres/person/day (lpd). This is considerably less than the UK average 141 lpd. So what is an 'average' person? Using the water calculator specified in building regulations I have estimated water consumption for this mythical individual using water efficient appliances versus a traditional context - by which I mean one from a few decades ago. Based on this estimate, even if all new homes use the most efficient appliances that would not be enough to keep Cambridge's usage within the allowed limits.

Here are the headline figures: the efficient house comes in at 104 lpd compared to 146 for the traditional house, and 47% of the difference is due to savings from flushing the WC. This chart compares the two.
Total use Efficient home 104 lpd, Traditional 146 lpd. For assumptions and use factors see below.

You might like to compare your usage with the 'average' person. If you use more then you could probably save more too.

Thursday, 12 October 2017

Can smart meters give us energy saving advice?

Would you like a smart meter that told you how much you can save by turning down your heating?  Current smart meters can't do this but researchers at the University of Bath reckon that it should be possible, with the aid of some extra sensors for temperatures and CO2 levels. They devised a system which could give you prompts such as 'We have noticed your thermostat is set to 23C. If you reduced the thermostat to 21°C you would save 11 kWh; this is equivalent to £1.43.'  (I think this must be per day and using electricity) [1]. They found that residents in their experiment were very likely to follow this advice. But all these extra sensors will be expensive - can we manage with less?