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| The Electric Vehicle Future: Where is all the power going to come from? |
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| GeorgeOfTheJungle:
--- Quote from: richard.cs on February 17, 2020, 11:50:59 am ---Below about 4 °C outside it switches to resistive heating with a corresponding efficiency hit. --- End quote --- People tend to forget that heat pumps don't work well when outside temps are below 0˚C because the (outside) evaporator turns into a frozen solid lump of ice: https://www.temperzone.co.nz/FAQ/Understanding-Defrost-Cycle/ |
| tom66:
--- Quote from: duak on February 16, 2020, 06:22:35 am ---Since an EV's drive electronics and batteries generate heat that has to be dissipated, does anyone know if any EV uses some of the waste heat to heat the passengers? Or even better, has a heat pump to heat/cool the passengers and electronics? --- End quote --- Yes, most EVs do this. As Mike points out, the heat isn't much, but on my Golf GTE, it's enough to keep the cabin at 20'C if the outside is at 15'C, for instance, and not require any input from the electric heater. On Teslas, the heat produced by the autopilot computer (100W+) is dissipated into the general cooling loop, which can be used for cabin heat if needed. The e-Golf comes with a heat pump, as do a few other EVs, however it's not that common. Apparently the compressor is about twice as large as a standard AC compressor, so the cost is likely higher (on the e-Golf it is an £800 option from memory.) That said, at full blast, the air con on my car pulls 3.2kW, which makes it somewhere around a 12,000 BTU system. That is about what you'd use for a small room heat pump so maybe there are other factors at play here, such as efficiency or non-flammable refrigerants. The Golf GTE is actually rather clever in terms of thermal design: there are three coolant loops, one for the engine, one for the EV motor and power electronics, and one for the battery and charger. It can cool the battery using the air conditioning, if you have a lead foot and are enjoying the hybrid sport mode a bit much, whilst scavenging heat from the engine if it is still warm after an extended drive. For that reason, on longer trips, I run the engine, then as I get to my destination, I switch to electric, which means the engine provides the cabin heat as it cools down for about 15 minutes or so. |
| nfmax:
Don't forget 'Negawatts', the decline in electricity consumption arising from improvements in efficiency of electricity-consuming devices. There is a short section on this in the latest issue of Drax Electric Insights (https://www.drax.com/wp-content/uploads/2020/02/200207_Drax_19Q4_Report_3.pdf) which reviews the changes in Great Britain's electricity system over the past decade: --- Quote ---Electricity demand has fallen steadily over the decade even though the population has grown 7% and GDP risen by a quarter in that time. Britain now consumes one-eighth less electricity, through a combination of shifting economic production, milder winters meaning less demand for electric heating, and improving energy efficiency. For example, a modern 42” LCD TV has triple the screen area of an old 21” square TV, but uses only half as much electricity. --- End quote --- The referenced data are a population growth from 62.8M to 66.9M, and a GDP growth from £1.7T to £2.2T (Office of National Statistics). Annual electricity demand fell by 13% over the decade (~332TWh to ~288TWh, from the graph in the report). Peak annual generation (including imports) looks to have been around 2005-2006. If this reduction arises from the causes claimed, it not only frees up generating capacity, but also distribution network capacity. Electric cars will need to be recharged at the same places where the old, power hungry TVs were used! On another (but related) topic from the report the carbon intensity of the UK generation mix has now fallen to the level where simple resistive electric heating produces less CO2 per kWh than the 'fleet average' domestic gas central heating boiler: --- Quote ---The move towards condensing boilers means the efficiency of the UK’s gas boilers is improving over time, but too slowly to help with climate change. The average efficiency of gas heating has risen from 82% to 86% over the last decade, meaning that the carbon emissions from producing 1 kWh of central heating or hot water only fell from 225 grams in 2010 to 215 grams in 2019. In comparison, standard electric heating would have produced 500 grams of CO2 per kWh2 of heat delivered back at the start of the decade, more than double that from a gas boiler. As electricity production has shifted away from fossil fuels, Britain has reached the point where it is cleaner to use electric heating than a gas boiler for the first time ever. Averaged over 2019, simple electric heaters produced 207 grams of CO2 per kWh of heat. We would now have to blend 12% hydrogen (by volume) into the mains gas grid for Britain’s boilers to be as clean as simple electric radiators. As the carbon intensity of electricity continues to fall, it will be impossible for hydrogen blending to keep pace with the carbon reductions, and only complete hydrogen switch-over will have the chance to compete on environmental grounds. --- End quote --- At current rates, it is about three times as expensive to heat using resistive electric heating compared with gas (though this ignores the lower maintenence costs of an electric system - no annual boiler service). It should be technically possible to blend up to 20% hydrogen into the current gas grid, without modifying existing gas-burning devices. Of course, this will only reduce overall CO2 emission if it is generated using 'clean' electricty, or in association with CCS. Eit to add disclaimer: A friend of mine is a director of Drax plc |
| tom66:
--- Quote from: CJay on February 18, 2020, 11:14:48 am ---I'm curious as to how charging is to work for a street full of terraced houses where nobody has allocated parking and charging cables would have to run across a public footpath? --- End quote --- Various options: - Charge at work if possible - Charge using a rapid charger at the supermarket/petrol station (like a regular car, just with a longer wait) - Charge using on-street charging furniture (e.g. Ubitricity in London have lamp-post chargers) The first two are easier to solve. On-street charging is a hard problem and requires a lot of investment. For most users though, a charge rate of 2-3kW would be sufficient for overnight charging. About 50% of people in the UK have access to driveways. EV charging is "easy" for these people, and they should be the initial target, as their demand for rapid, destination and work charging will allow others without off-street parking to charge. When away from home, I have trailed cables under cable protectors across the street to charge my car, which is a technique that is actually endorsed by Hampshire County Council: https://www.hants.gov.uk/transport/ev-charging-points/ev-charging-guidance |
| nfmax:
--- Quote from: tom66 on February 18, 2020, 11:30:39 am --- --- Quote from: CJay on February 18, 2020, 11:14:48 am ---I'm curious as to how charging is to work for a street full of terraced houses where nobody has allocated parking and charging cables would have to run across a public footpath? --- End quote --- Various options: - Charge at work if possible - Charge using a rapid charger at the supermarket/petrol station (like a regular car, just with a longer wait) - Charge using on-street charging furniture (e.g. Ubitricity in London have lamp-post chargers) The first two are easier to solve. On-street charging is a hard problem and requires a lot of investment. For most users though, a charge rate of 2-3kW would be sufficient for overnight charging. About 50% of people in the UK have access to driveways. EV charging is "easy" for these people, and they should be the initial target, as their demand for rapid, destination and work charging will allow others without off-street parking to charge. When away from home, I have trailed cables under cable protectors across the street to charge my car, which is a technique that is actually endorsed by Hampshire County Council: https://www.hants.gov.uk/transport/ev-charging-points/ev-charging-guidance --- End quote --- The whole idea of being allowed to store your personal possessions on public property (i.e. leaving your car permanently parked on a public road) might perhaps be reconsidered... |
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