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Is it time to ask UKPN to consider if HVDC works better in future networks ?

I have been wondering about the big line losses that are necessary in HV transmission systems , HVDC can nearly halve these to 4% but all the new renewable technology of generation and of storage is mostly DC . From the interconnector its all AC cant really change that , but if the electric car becomes reality then all the chargers will be converting DC to AC (in some quite high flows of electricity from low to full of some batteries) , so we are perhaps saying that the electric car will bring more line losses , it might not be that bigger deal, but if we electrolyse water to Hydrogen and Oxygen then the conversion losses from AC to DC will add up , so it has to be better to just transmit in DC , if we could generate in DC and I think we have brushless three phase generators now then we generate and transmit efficiently to the new big users of electricity . In the USA we see generation plant to city interconnector , I don't think they use a balancing grid , as cities are so far apart . I know any design has its problems but with the new uses of electricity any generation system will have to match (or think about the new denands) , its perfrectly possible to have designed and balanced generator to interconnector supply , but a shared transmission grid obviously allows you to arrange supply generator and demands in a different way .

One use I thought about is for a village to say have a battery and the line to it may only charge the battery once a week as DD line to DC battery and that electricity that is then spare can be used to say make Hydrogen ? It could give a completely different and more efficienct system ? Not really worked much on HV systems , but I can sort see a sketch of how it could work as a network . If only a short distance to a big demand then might as well use AC , but a 1000mw supply to an interconnector losing 7% over its life time is a lot .

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0 Helios over 3 years ago

oh I agree at over 1000km other non electrical transmission systems start to be more efficient , but at under 1000km (remembering we now have much more design efficiency to think about with DC and moving and storing DC ) it should win out , for instance if you have a 100kw low head hydro , it has a higher availability than a 100kw wind turbine , both will generate in DC and if you want to store electricity as electricity , then its a DC battery , that is the most efficient electrical system , to feed say a small town , in turn the new demand for electric cars will be the biggest use of electricity from domestic supplies and the conversion losses will be important over time , so for a small village/town using a renewable it may be better if they charge there cars from the large battery . What I mean is with the electric car we will have very large use of DC electricity so it starts to change thinking on grid design and if we want to create Hydrogen from water electrolysis , this will also be using high amounts of DC electricity , for example a hydrogen car will do 400miles on 5kg of H2 , so at 60 kwh for 1 kg of hydrogen , 350 kw/hr (note conversion loss of electrolysis cell efficiency and efficiency of Hydrogen fuel cell, which are rarely quoted , which electric car companies see as the end game with Hydrogen as battery to electric motor is 80%), then a town of 1000 cars (doing 200 miles each) will need 175,000 kwh of new DC electricity each week , if a house uses 50 kwh of non car charging electricity each week , you can see that this new demand for the electric car is of a different order and well worth thinking about grids differently. Electrolysis DC electricity requirements are so high that efficiency becomes really important .
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0 Helios over 3 years ago

oh I agree at over 1000km other non electrical transmission systems start to be more efficient , but at under 1000km (remembering we now have much more design efficiency to think about with DC and moving and storing DC ) it should win out , for instance if you have a 100kw low head hydro , it has a higher availability than a 100kw wind turbine , both will generate in DC and if you want to store electricity as electricity , then its a DC battery , that is the most efficient electrical system , to feed say a small town , in turn the new demand for electric cars will be the biggest use of electricity from domestic supplies and the conversion losses will be important over time , so for a small village/town using a renewable it may be better if they charge there cars from the large battery . What I mean is with the electric car we will have very large use of DC electricity so it starts to change thinking on grid design and if we want to create Hydrogen from water electrolysis , this will also be using high amounts of DC electricity , for example a hydrogen car will do 400miles on 5kg of H2 , so at 60 kwh for 1 kg of hydrogen , 350 kw/hr (note conversion loss of electrolysis cell efficiency and efficiency of Hydrogen fuel cell, which are rarely quoted , which electric car companies see as the end game with Hydrogen as battery to electric motor is 80%), then a town of 1000 cars (doing 200 miles each) will need 175,000 kwh of new DC electricity each week , if a house uses 50 kwh of non car charging electricity each week , you can see that this new demand for the electric car is of a different order and well worth thinking about grids differently. Electrolysis DC electricity requirements are so high that efficiency becomes really important .
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Is it time to ask UKPN to consider if HVDC works better in future networks ?

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