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A Dutch company has launched a new type of wind turbine that is small enough to fit onto the roof of a house. The turbine looks like a Nautilus shell, and their website explains how it works:
Most today's wind turbines require that a difference in pressure between the front and the rear side of the rotor blades be maintained in order to be effective. However, this difference in pressure also has a negative effect called "drag".
Our turbine rotor captures the kinetic energy of the wind due to its speed, and, by reversing the wind and reducing it to almost zero Beaufort converts it into mechanical energy. By doing this the wind speed's effect (in kinetic energy) on the rotor is maximized and "lift" is obtained by the wind's acceleration over the rotor plane.
(Score: 2, Informative) by Zinho on Monday June 02 2014, @07:06PM
The write-up provided is useless to an engineer (or anyone willing to spend two seconds thinking about what was said). There is no way to eliminate drag and still extract energy from the air stream. If you take Kinetic Energy (1/2 mV^2) out of the wind you slow it down, so there is going to be drag involved.
The most informative statement they made was that their turbine has "80 percent of the maximum that is theoretically feasible." The theoretical maximum referred to is Betz's law [wikipedia.org], "no turbine can capture more than 16/27 (59.3%) of the kinetic energy in wind." So this new design will extract .593*.8 = .474 -> 47.4% of the kinetic energy from the incoming wind.
That's not bad, actually; in fact, that's the sort of efficiency you get on large wind installations. It's obvious to me that the designer either doesn't really understand the physics of what they're involved in, or that they've been told to shut up and let the marketroid talk to the Eloi. That's kind of tragic, since it seems to me that they have a good product and it can probably stand on its own without hyperbole or outright lies to support it.
I should also note that the 1300 KWh rating they gave is per year, and that they're estimating that two or three of these would satisfy the needs of a typical Dutch household. I should really get on whatever efficiency program they're using, since my consumption is about that much per month (more in the summer). This would be cool to put on my roof as a way to start loud conversations with my neighbors, but it wouldn't be very cost-effective as a way to offset my power usage.
"Space Exploration is not endless circles in low earth orbit." -Buzz Aldrin
(Score: 2) by HiThere on Monday June 02 2014, @08:05PM
Well, they said two or three plus solar cells. Didn't mention batteries for some reason. Even if I assume that everything the said is accurate, and that two or three plus solar cells (how many?) would generate enough energy, there's no mention of how you deal with when the sun's not shining AND the wind's not blowing.
So, yes, it's marketdroid speak. Any engineer would have known that it was misleading no matter HOW poor an engineer he was. Either that, or it's an incredibly bad translation that just happened to be grammatical.
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(Score: 2) by hankwang on Monday June 02 2014, @09:52PM
"1300 KWh rating they gave is per year, and that they're estimating that two or three of these would satisfy the needs of a typical Dutch household. I should really get on whatever efficiency program they're using, since my consumption is about that much per month (more in the summer)."
We (2 person household in Netherlands, 95 m2/1000 sq.ft house) use around 1800 kWh/yr, of which we generate about 600 kWh from a small solar panel. How? We rarely use airconditioning, which is bearable because daytime temperatures exceed 30 C only a few days per year and because this house is well insulated both for keeping the heat in during the winter, and out during the summer. Fridge/freezer is energy class A+++ (150 kWh/yr), washer is about 0.6 kWh per 7 kg cycle (1x per week), dishwasher 1 kWh/cycle (3x per week), nearly all lighting is CFL and LED, and generally I pay attention to idle/standby power use of various electronics (including fileserver), keeping in mind that every watt-year costs 2 euros, so many things are switched off when not in use or are purchased with energy use as a criterion. The tv is only on if we're actually watching; it's not used as a moving wallpaper (I've the impression that that is common in the US). For heating and cooking we use natural gas. I suspect that the water pump for the central heating system takes a big chunk of those 1800 kWh. Our computing needs are served by various mobile devices and smallish laptops, and a small server (14 W idle).
It also helps that we both have fulltime jobs.
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(Score: 0) by Anonymous Coward on Monday June 02 2014, @11:15PM
"For heating and cooking we use natural gas."
There's your problem. Your energy accounting is dishonestly hiding a sizable chunk of your use in a fossil fuel you forgot to account for.
(Score: 1) by Zinho on Tuesday June 03 2014, @12:40AM
In the context of reducing electrical usage I think it's fair to consider natural gas use as a viable alternative. I cook year round and heat in the winter with gas, too; I'd use a gas clothes dryer as well if I could. We recently switched to using a clothesline to dry clothes, and we're down to about 1,000 kWh/month if we don't run air conditioning.
I think the biggest difference between us is location - I'm in south central United States, and hankwang is in the Netherlands. Where I live we average 18 days above 100F (37.5C), and in 2011 we had 71 days above that temperature. I'm curious about the water pump for the heater, is that radiant flooring?
In any case, hankwang is using close to 10% of the electricity I am. That's astounding to me. I'll have to look at my appliances to see if there are savings I could make there.
"Space Exploration is not endless circles in low earth orbit." -Buzz Aldrin
(Score: 2) by carguy on Tuesday June 03 2014, @11:52AM
Another data point, we are two people working from home, a couple of laptops on all the time. The water boiler (baseboard heat) and hot water heater run on gas, everything else is electric. Location is downwind of Lake Erie in a 1963 brick ranch. The only insulation that it was easy to add was to take the attic floor up to a total of 18" (~0.4 meter) of fiberglass. It has never hit 100F here, although with warming it may get there soon. These factors both moderate summer temps and usually limit A/C (a smaller unit, but not energy star) to a few hours in summer evenings. The basement has a small de-humidifier running about half time in the summer to control mold. We mostly cook meals at home, eat dinner out once or twice a week. A recent "energy star" fridge made a big difference compared to the previous fridge from the 1980s. We are both good about turning lights off, but for reading in the evening hours still use 100W incandescents (eyestrain from CFLs); looking forward to trying brighter LED "bulbs". We dry about half the clothes on a rack indoors, more in winter for the humidifying effect.
I'm looking at putting the cable box (a constant draw) on a timer, so it boots up before our typical TV watching in the evenings--but it would be more convenient if the cable company had a box that idled at lower power. If we renovate the kitchen/utility area we will change over to a gas range (cooktop) and oven, as well as a gas clothes dryer.
We're currently around 400 kWh/month (yearly average) including A/C for a few months in summer. If we average the 8 or 9 "non-A/C months" it's just under 300 kWh/month. It would be hard to get down to the hankwang / Netherlands level here, but we do have room for improvement.
(Score: 2) by hankwang on Wednesday June 04 2014, @09:42AM
Regular radiators/convectors; the pump to get the water from the heater (Boiler? Not sure about the US/English terms) to the radiators takes about 100 W when it's running. The heater recovers heat by condensing the water out of the exhaust gases, but this will work best if it operates at low temperatures. I try to maximize efficiency by keeping the water temperature as low as possible (70 C/158 F when it's freezing, 50 C/122 F during spring/autumn). The penalty is that the pump has to run for more hours. When we use hot tap water, the same heater will heat up the water in the closed heating circuit, and use a heat exchanger to heat up tap water; also then, the pump will run. No hot water is stored when the tap is not running. This is a very common setup here in Netherlands; I'm not sure how domestic heating works in the US. Coming winter, I'll try to do some optimization on the electricity/gas usage of the heater. :-)
An energy meter (I think they're called Kill-a-Watt in the US) and a notebook can be very revealing. A colleague of mine discovered that his fancy espresso machine, which was switched on all day during the weekends, was a huge power drain. Our home is exceptional as it has an a/c system (inherited from the previous owner); when I discovered that it uses 130 kWh/yr on standby, I installed a 4-euro switch and saved 26 eur/yr in electricity.
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(Score: 2) by demonlapin on Tuesday June 03 2014, @12:07AM
(Score: 2) by evilviper on Tuesday June 03 2014, @04:15AM
1) Their climate is much milder than you'd expect, compared to ANYWHERE in America. The Atlantic ocean does miracles for Europe's climate...
2) The more people you cram into a smaller space, the less active heating you need (and the more active cooling). Cheaper land/housing costs in the US have lead to a proliferation of larger homes. If we just had smaller houses like Europe, it would go a long way towards reducing heating costs.
3) Heat-pumps cost as little as $600 (basic split system), and can QUADRUPLE (COP=3.9) the efficiency of (electric) heating, versus old resistive heating coils. It can be cheaper than natural gas, and split systems make it extremely easy to retrofit old buildings. For cooling, a swamp cooler can be drastically cheaper in any location where humidity isn't high.
4) More insulation helps a lot. Big, unshaded, south-facing windows can add a LOT of heat to your house. etc.
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