MM,
Before we get too exited about savings by using DC instead of AC, we might look at where and why we have this large differences in the energy use by appliances. Let us first establish the fact that a conversion as such, will cost us between 3 to 10%, depending on method, size and application. When you talk about appliances, we should also include the AC/Heat pump unit in this and very large savings can be done. The losses are more created by the use of electrical engines/compressors, than by the use of alternate current or direct current. The large differences in energy use does not come from the type of current, but from the way the capacity control is done. The revelation control in AC engine used in the appliances is governed by the fixed AC frequency and the capacity control is done by starting and stopping the compressor. The revelation control in the DC engine is governed by voltage/current and the capacity control is done by varying the speed/force of the engine. Since you already are very familiar with electrical engines, you are probably ahead of me now, about the consequences of the different methods. I will anyway mention that the consequences can be somewhere between 30 to 45% more energy use by the capacity control of the AC engine. After the conversation losses, we end up with around 25-30% difference in energy use for appliances. In the past it was very large differences cost and durability between the AC and DC engines, in favor to the AC engines. By new development, these differences are no longer an critical issue and the energy use have started to be the absolute critical issue for certain engine applications. If you look at losses in distribution of DC, we must agree with the much higher efficiency of AC. One very important issue is also the security aspects, which more or less totally disqualifies high voltage DC in homes and for general use in appliances. It is better and more manageable of security design, if the conversion is done in the appliance and close to the engine. The large loss of lives, that a general high voltage DC distribution would cause, is not worth it. Hakan At 22:13 16/03/2004, you wrote: >On Mon, 15 Mar 2004 23:48:36 -0800 (PST), you wrote: > > > > >Monday, March 15/04 > >murdoch <[EMAIL PROTECTED]> wrote: > > > >>What about the issue of efficiency in converting from AC >to DC and > >>then back to AC? > > > >>Each of these conversion actions may have > >>consequences in terms of lost energy, but I haven't yet >figured out > >>the losses. This has come up for me recently, so it's >on my mind. > > > >According to an "Inverter comparison chart," supplied by West Marine > Co. Maximum efficiency of the inverters they list range from 88% to > 94%. All of the products that they list appear to be made by Xantrex, > (Heart Interface, Trace Engineering and Statpower are all now owned by > Xantrex making them probably the biggest manufacture of > inverters). Many of these products have built in battery chargers. I > don't know if the efficiency of the charging circuit is equal to that of > the inverting circuit. I don't have efficiency data on chargers. > > > >If we assume that a good charger will deliver about 90% efficiency on > the conversion from 120 VAC to DC, and a good inverter will deliver about > 90% back to AC, you can expect to lose about 20% in conversion. > > > >I hope this helps put you in the ballpark regarding efficiency. > >Yes, it does help, thank you. I was looking into a converter, to go >from AC to DC, because there is a DC refrigerator out there >(Sundanzer) that appears to be so efficient that I thought it might be >worthwhile to consider. > >The price for an AC-to-DC converter was reasonable, but the salesman >wasn't 100% sure about efficiency losses. We made sort of a little >side-project about this, because nobody had really asked these >questions before, and they're just starting to sell Sundanzer, >alongside Equator and Sun Frost. > >He got a figure of 5% that we used as a sort of stop-gap. But I think >to be safe, I'd add a bit more on to that 5%, and that "bit-more" >jibes with your research. > >In the end, I think I'm going to get a Sun Frost RF-12, and eschew the >separate Fridge-separate-freezer idea. I had that thought because >there are times when I want a fridge but don't use a Freezer that >often, and the savings of unplugging the freezer could be substantial? > >The Sun Frost is super-expensive compared to a decent small Energy >Star Conventional Fridge I could buy at Home Depot, but it's still >about twice-or-more efficient, and might in the end save me enough >energy to save me money. And since it's AC, I'll be able to avoid >this inconvenience of changing over my whole house to this or that. > >Sundanzer does have this one wild product... a fridge that is designed >to operate solely on a modest (90-120 watts?) solar array in certain >types of regions without any batteries at all: > ><http://www.sundanzer.com/PDF/SunDanzer_Batt_Free_Tech_Sh.pdf>http://www.sundanzer.com/PDF/SunDanzer_Batt_Free_Tech_Sh.pdf > >MM Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Biofuels list archives: http://infoarchive.net/sgroup/biofuel/ Please do NOT send Unsubscribe messages to the list address. To unsubscribe, send an email to: [EMAIL PROTECTED] Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/biofuel/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
