July 2010 -

The issue of kinetic road plates came up again today. Doesn’t it sound like a great idea – harvest energy from cars passing over a compressible ramp in the road to drive a generator? Free energy, as long as people keep driving cars.

But hang on – where is this free energy coming from?

Well, since energy cannot be created nor destroyed, it clearly must come from the car’s engine as the only power supply in the vicinity. In order to compress the ramp the vehicle must first drive up it’s incline. The increase in gravitational potential energy created by raising the mass of the car is then converted to kinetic energy as the ramp gently compresses and drops the car back down to road level, driving a generator to create electricity. But, in order to raise the car up the ramp in the first place consumes more fuel, exactly like driving up a hill.

So, rather than harvesting free energy, the kinetic plate is actually stealing a little bit of energy from each car passing over it. That energy must be replaced by burning more fuel; it’s just that the amount of fuel taken from each car is so small that you’d be unlikely to notice.

Now one of the first adopters of this technology is a national supermarket chain – very clever – the supermarket also sells fuel from its own petrol station, so they are onto a double winner. The store gets a free supply of energy from its customers and then sells more energy to the same customers to replace the energy it has stolen from them.

Someone mentioned to me the other day that it was next to impossible to find a new washing machine with both hot and cold fill. So how are we supposed to reduce carbon emissions from domestic laundry by using water from low carbon sources such as solar thermal?

To check whether this was true, I did a quick survey online. Of the 50 top selling washing machines from 13 different manufacturers, none has the option to fill with hot water. Yet all of these machines are A or A+ rated for energy efficiency. I wondered why this had come about, so I did a bit of further research.

The Energy Information (Washing Machines) Regulations 1996 is the UK enactment of the EC Directive on the energy labeling of domestic appliances. These explicitly state that “These Regulations shall apply only to appliances which are electric mains operated and unable to use other energy sources”

The second bit of this statement is the significant one. In order to deliver a universal rating system it must be possible to compare like for like. How could you compare the efficiency of an electrically heated machine with one that receives hot water from an external source of unknown quality. This little get out clause is clearly included to ensure that the energy efficiency ratings will be equivalent across the board. What this means in practice of course is that a washing machine with a hot fill cannot be given an energy label.

Now when it comes to heating water, even a conventional boiler will do it with less carbon emission than an electric heating element in a washing machine. Since energy labels are mandatory this little sentence, buried in the verbiage, creates a prohibition on what are potentially the most carbon efficient washing machines.

The washing machine manufacturers must have been delighted. As the sale of appliances without energy labels was prohibited they no longer needed to include a second set of water control valves in their machines, thus reducing manufacturing costs. I don’t suppose that the savings were passed on to consumers, but just try to get them to add back the hot fill now without putting the price up.

Then we have to factor in the fact that the energy label rating is based on a very specific wash cycle, whilst consumers apparently are tending to use more energy intensive quick wash cycles. According to a number of studies the electricity consumption for laundry is much higher than would be inferred from the energy labels.

In the UK, Building Regulations and policies like the Renewable Heat Incentive are designed to reduce carbon emissions in building services installations, including hot water generation. Washing machines are excluded from these policy instruments because they are already covered by the energy labelling regulations. But water heating is water heating and probably best dealt with as an efficient integrated system, not in isolation in your washing machine.

So, in drafting regulation which is supposed to promote energy efficiency the European Union scribes have actually written one that prohibits the most carbon efficient means of operation. Maybe one day our Governments will consult people who understand the issues before writing new laws.

Monthly Archives: July 2010

Kinetic Road Plates

Unintended Consequences