where does came the idea that DC is safer ? as engineer during high power electronic course I was clearly taught that 100V DC was sure deadly with no chance to survive (you get stuck on the wire until you die), while 220AC is quite forgiving with a chance to escape 100 time a second...
is that what edison succeeded in spreading ? anyway for modern electronic DC is better, but the voltage have to be standardised. will you have 12V, 18V, 24V DC, or 100V DC or 400V DC... it seems in cars the bus is moving from 12V and 24V to 48V, to save energy... (at the expense of life?) AC is good with transformers and sync/async rotating machine. DC is better with switched power and brushless rotating machine. but you can kill a human with 24V DC in wet condition, 50V dry... at least twice is required with AC note also that installing a differential is harder/moreexpensive with DC than with AC (I agree it is possible, and maybe affordable soon with modern electronics, not far from smart meter cost) 2015-01-18 2:29 GMT+01:00 Jed Rothwell <[email protected]>: > Axil Axil <[email protected]> wrote: > > >> Humanity will continue to migrate into the city from the remote >> countryside Cities will house people in high concentrations. >> > > In high concentrations, central generators may remain cost effective for a > while. Eventually, all machines will have built in cold fusion power > supplies. There will be no distribution of electricity anywhere, not even > in your house. > > Arthur Clarke predicted that cold fusion home generators will be DC, not > AC, because it is a lot safer. You cannot distribute DC electricity with a > power company, and transformers are wasteful and expensive. > > Cold fusion power generators can be cogenerators, replacing central > heating or hot water heaters, at practically no additional cost. > > > >> Power production will continue to be grid based and connected to huge >> power stations where economies of scale will rule the day. >> > > Economy of scale does not work when scaling up costs more than scaling > down! That is why we have microcomputers nowadays instead of mainframe and > minicomputers. Even giant computers are made up of small ones in an MPP > configuration. Starting around 1980, small computers become more cost > effective than large ones. It was the "economy of scale" reversed -- the > smaller, the cheaper per FLOP or storage space. > > The same thing happened to rural passenger rail transportation after the > introduction of the Model T. It soon became cheaper to drive a car than to > ride in a train or trolley car. Only large urban short range passenger > service survived. Automobiles are scaled down from railroad locomotives. > They are decentralized. They are not only cheaper, but far more convenient. > Cold fusion home generators will ultimately be far cheaper, more reliable > and more convenient than central electric power distribution. > > Also, many applications that now use electricity will use cold fusion heat > directly. These include space heating, water heating, air conditioning and > refrigeration, clothes drying, process heating and so on. About 8% of all > energy used in the home. See chapter 15 of my book. > > - Jed > >
