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High-Voltage DC Breakthrough Could Boost Renewable Energy

57 points by amalag 14y ago

dkhenry 14y ago
If I am not mistaken we already use HVDC on high power runs due to its much lower loss ? How does this beaker change that ?
- surbas 14y ago
  According to the article HVDC is only used for point to point electrical runs, because managing grids of it is very hard. What the breaker does is allow for easier managing of the grids by allowing parts under going surge, like from a lighting strike, to be segmented off.
  - crusso 14y ago
    Exactly. The modern AC power grid is very resilient due in part to the multi-interconnect nature which allows for parts of the grid to go down without taking down the whole network. On an AC grid, there are breakers that automatically disconnect and often reconnect. http://en.wikipedia.org/wiki/Recloser http://en.wikipedia.org/wiki/Recloser I guess that this HDVC hybrid breaker accomplishes more or less the same thing.
- kens 14y ago
  A friend's father worked on a massive DC power line project in Manitoba in the 1960s [1], so HVDC technology has been around for a long time. The article discusses a potential incremental improvement that might make HVDC useful in more circumstances, but the article seems to be making HVDC sound like a big new breakthrough. [1] http://en.wikipedia.org/wiki/Nelson_River_Bipole http://en.wikipedia.org/wiki/Nelson_River_Bipole
- gus_massa 14y ago
  DC is better for very long distances and underwater connections: http://en.wikipedia.org/wiki/High-voltage_direct_current http://en.wikipedia.org/wiki/High-voltage_direct_current
EEGuy 14y ago
DC doesn't have phase and frequency issues AC does. Presumably a shared DC grid would be constant-voltage. What surprises naive me is that gigawatt inverters seem to be a done deal. Once we have gigawatt-hour ("utility-") scale storage, then we can have a fully renewables-based future (again, naive me thinks).
- stcredzero 14y ago
  The government should be building out infrastructure like this.
  - sageikosa 14y ago
    Or maybe someone who could profit from it.
    - yarrel 14y ago
      Rent seeking doesn't lead to innovation.
      - sageikosa 14y ago
        Hence why the government shouldn't be involved. I live in a state (Pennsylvania) with energy choice. The one with the most "efficient" system gets the lowest rates, which allows me to preserve my own little slice of the "social wealth". If I so choose, I can go for an eco-friendly solution as well, if that sort of thing made me feel good.
        stcredzero 14y ago
        By this logic, the interstates, the railroads, and the internet should not exist.
        CapitalistCartr 14y ago
        That makes no sense. First, he's advocating private ownership of electrical infrastructure, not the elimination of it. Built by private interests doesn't equate to non-existence. Second, advocating private ownership of electrical infrastructure doesn't equate advocating private creation and ownership of all infrastructure. I rather like a good straw man; this one isn't.
marshray 14y ago
Ohms law: V = IR Power: P = VI Power loss due to resistive heating in the wires: P = I^2 * R Note that current (I) quickly dominates the loss calculation because it is squared. So for transmission lines, efficiency is obtained by keeping the current as low as possible. Therefore, to transfer the same power you need to make the voltage as high as possible. The I^2*R heating loss applies equally to DC and AC transmission lines. So the DC lines still need to be high voltage for efficiency as well. By using AC we can 'transform' high-voltage-low-current to low-voltage-high-current power very easily. It's literally just two coils of wire around a chunk of iron. Step-down AC transformers are used both at your neighborhood substation and on the pole outside your house. But the article didn't say how they planned to transform the high-voltage-low-current DC into anything usable.
- eigenvector 14y ago
  A switch-mode DC/DC converter obtains the same result as an AC transformer with efficiency approaching that of a well-designed AC transformer. It is a solved problem.
  - marshray 14y ago
    The century-old methods are still competitive at this high a voltage and power. http://en.wikipedia.org/wiki/High-voltage_direct_current#Disadvantages http://en.wikipedia.org/wiki/High-voltage_direct_current#Dis... HVDC is less reliable and has lower availability than alternating current (AC) systems, mainly due to the extra conversion equipment. Single-pole systems have availability of about 98.5%, with about a third of the downtime unscheduled due to faults. Fault-tolerant bipole systems provide high availability for 50% of the link capacity, but availability of the full capacity is about 97% to 98%.[19] The required converter stations are expensive and have limited overload capacity. At smaller transmission distances, the losses in the converter stations may be bigger than in an AC transmission line. The cost of the converters may not be offset by reductions in line construction cost and lower line loss.
- breckinloggins 14y ago
  I'm wondering if it would be cost-feasible (eventually) to incorporate pure sine wave inverters at the "last mile point" and do AC to the premises. Does anyone know?
CapitalistCartr 14y ago
I would love to have my house run on DC. Almost everything I own either switches to DC internally, or doesn't care. If it were practical to run the grid on DC, or we all go to solar for residential and light commercial, maybe I'll get my wish.
- stcredzero 14y ago
  Just do it! http://en.wikipedia.org/wiki/Nickel%E2%80%93iron_battery http://en.wikipedia.org/wiki/Nickel%E2%80%93iron_battery
  - Wingman4l7 14y ago
    Interesting -- I'd never heard of this battery tech -- but I thought most personal off-grid battery banks were lead acid. Google "lead acid vs nickel iron" and you'll get some discussions on solar power / off-grid forums. I skimmed these, and it seems like any advantage nickel iron has doesn't justify their greater cost.
- grecy 14y ago
  Tons of people up here have elaborate solar setups, usually 24V or 48V DC. Then they have an expensive 4kW inverter to 110V AC, and the vast majority of their appliances just convert back to 12V DC. A big plan for my off-grid setup is straight DC.
  - meaty 14y ago
    A big chunk of your energy will disappear in heat via resistance unless you run silver wire everywhere or keep the runs short. DC cabling has some weird voltage divider and load characteristics as well causing drop outs. This is particularly visible with high current, low voltage loads. 48v dc is pretty dangerous as well.
- gvb 14y ago
  The stuff in your house that "switches to DC internally" isn't switching to 100,000 to 800,000 volts[1], which is what the HVDC is that the article is talking about. Running DC in your house isn't going to eliminate any voltage conversions that are already going on, they will just be DC-DC converters with 48vDC (or whatever) input rather that 120vAC input. Most of the stuff in your house isn't even running on the same voltages internally... most of the electronics nowadays use many voltage "rails": * 17-19v laptop chargers (the voltage has to be higher than the battery's voltage in order to charge the battery) * 12v for older hard drives * 5v for not quite so older hard drives and older logic * 3.3v for newer logic and newer hard drives * A veritable plethora of sub-3.3v rails for CPU chips and other high tech chips. * 120vDC for "universal" motors unless you replace all your appliance motors with 48vDC (or whatever) motors In addition, the current requirements of running at a non-lethal DC voltage inside your house would require much larger wire gauges than your current wiring in order to keep the resistive losses reasonable[2]. The rewiring costs would be staggering. [1] http://en.wikipedia.org/wiki/High-voltage_direct_current http://en.wikipedia.org/wiki/High-voltage_direct_current [2] Charts for 12v wiring, 48vDC would be 4x better, but still not good - http://www.westmarine.com/webapp/wcs/stores/servlet/WestAdvisorView?langId=-1&storeId=11151&catalogId=10001&page=Marine-Wire http://www.westmarine.com/webapp/wcs/stores/servlet/WestAdvi...
amalag 14y ago
I didn't follow why the article stated that AC is not ready for the grid of the future. This DC grid seems to be an incremental improvement, 10%? But IMO not a huge breakthrough.
specialist 14y ago
When I was a kid, Scientific American had a cover featuring a high voltage transistor, which was supposed to revolutionize power transmission. My very weak understanding is that energy transmission is directed by a delicate balancing of loads. Which is inefficient. Where using a solid state switching solution would be more efficient. Does this sound familiar to anyone?

57 points by amalag 14y ago

If I am not mistaken we already use HVDC on high power runs due to its much lower loss ? How does this beaker change that ?

surbas 14y ago
According to the article HVDC is only used for point to point electrical runs, because managing grids of it is very hard. What the breaker does is allow for easier managing of the grids by allowing parts under going surge, like from a lighting strike, to be segmented off.
- crusso 14y ago
  Exactly. The modern AC power grid is very resilient due in part to the multi-interconnect nature which allows for parts of the grid to go down without taking down the whole network. On an AC grid, there are breakers that automatically disconnect and often reconnect. http://en.wikipedia.org/wiki/Recloser http://en.wikipedia.org/wiki/Recloser I guess that this HDVC hybrid breaker accomplishes more or less the same thing.
kens 14y ago
A friend's father worked on a massive DC power line project in Manitoba in the 1960s [1], so HVDC technology has been around for a long time. The article discusses a potential incremental improvement that might make HVDC useful in more circumstances, but the article seems to be making HVDC sound like a big new breakthrough. [1] http://en.wikipedia.org/wiki/Nelson_River_Bipole http://en.wikipedia.org/wiki/Nelson_River_Bipole
gus_massa 14y ago
DC is better for very long distances and underwater connections: http://en.wikipedia.org/wiki/High-voltage_direct_current http://en.wikipedia.org/wiki/High-voltage_direct_current

EEGuy 14y ago

DC doesn't have phase and frequency issues AC does. Presumably a shared DC grid would be constant-voltage. What surprises naive me is that gigawatt inverters seem to be a done deal. Once we have gigawatt-hour ("utility-") scale storage, then we can have a fully renewables-based future (again, naive me thinks).

stcredzero 14y ago
The government should be building out infrastructure like this.
- sageikosa 14y ago
  Or maybe someone who could profit from it.
  - yarrel 14y ago
    Rent seeking doesn't lead to innovation.
    - sageikosa 14y ago
      Hence why the government shouldn't be involved. I live in a state (Pennsylvania) with energy choice. The one with the most "efficient" system gets the lowest rates, which allows me to preserve my own little slice of the "social wealth". If I so choose, I can go for an eco-friendly solution as well, if that sort of thing made me feel good.
      - stcredzero 14y ago
        By this logic, the interstates, the railroads, and the internet should not exist.
        CapitalistCartr 14y ago
        That makes no sense. First, he's advocating private ownership of electrical infrastructure, not the elimination of it. Built by private interests doesn't equate to non-existence. Second, advocating private ownership of electrical infrastructure doesn't equate advocating private creation and ownership of all infrastructure. I rather like a good straw man; this one isn't.

marshray 14y ago

Ohms law: V = IR Power: P = VI Power loss due to resistive heating in the wires: P = I^2 * R Note that current (I) quickly dominates the loss calculation because it is squared. So for transmission lines, efficiency is obtained by keeping the current as low as possible. Therefore, to transfer the same power you need to make the voltage as high as possible. The I^2*R heating loss applies equally to DC and AC transmission lines. So the DC lines still need to be high voltage for efficiency as well. By using AC we can 'transform' high-voltage-low-current to low-voltage-high-current power very easily. It's literally just two coils of wire around a chunk of iron. Step-down AC transformers are used both at your neighborhood substation and on the pole outside your house. But the article didn't say how they planned to transform the high-voltage-low-current DC into anything usable.

eigenvector 14y ago
A switch-mode DC/DC converter obtains the same result as an AC transformer with efficiency approaching that of a well-designed AC transformer. It is a solved problem.
- marshray 14y ago
  The century-old methods are still competitive at this high a voltage and power. http://en.wikipedia.org/wiki/High-voltage_direct_current#Disadvantages http://en.wikipedia.org/wiki/High-voltage_direct_current#Dis... HVDC is less reliable and has lower availability than alternating current (AC) systems, mainly due to the extra conversion equipment. Single-pole systems have availability of about 98.5%, with about a third of the downtime unscheduled due to faults. Fault-tolerant bipole systems provide high availability for 50% of the link capacity, but availability of the full capacity is about 97% to 98%.[19] The required converter stations are expensive and have limited overload capacity. At smaller transmission distances, the losses in the converter stations may be bigger than in an AC transmission line. The cost of the converters may not be offset by reductions in line construction cost and lower line loss.
breckinloggins 14y ago
I'm wondering if it would be cost-feasible (eventually) to incorporate pure sine wave inverters at the "last mile point" and do AC to the premises. Does anyone know?

CapitalistCartr 14y ago

I would love to have my house run on DC. Almost everything I own either switches to DC internally, or doesn't care. If it were practical to run the grid on DC, or we all go to solar for residential and light commercial, maybe I'll get my wish.

stcredzero 14y ago
Just do it! http://en.wikipedia.org/wiki/Nickel%E2%80%93iron_battery http://en.wikipedia.org/wiki/Nickel%E2%80%93iron_battery
- Wingman4l7 14y ago
  Interesting -- I'd never heard of this battery tech -- but I thought most personal off-grid battery banks were lead acid. Google "lead acid vs nickel iron" and you'll get some discussions on solar power / off-grid forums. I skimmed these, and it seems like any advantage nickel iron has doesn't justify their greater cost.
grecy 14y ago
Tons of people up here have elaborate solar setups, usually 24V or 48V DC. Then they have an expensive 4kW inverter to 110V AC, and the vast majority of their appliances just convert back to 12V DC. A big plan for my off-grid setup is straight DC.
- meaty 14y ago
  A big chunk of your energy will disappear in heat via resistance unless you run silver wire everywhere or keep the runs short. DC cabling has some weird voltage divider and load characteristics as well causing drop outs. This is particularly visible with high current, low voltage loads. 48v dc is pretty dangerous as well.
gvb 14y ago
The stuff in your house that "switches to DC internally" isn't switching to 100,000 to 800,000 volts[1], which is what the HVDC is that the article is talking about. Running DC in your house isn't going to eliminate any voltage conversions that are already going on, they will just be DC-DC converters with 48vDC (or whatever) input rather that 120vAC input. Most of the stuff in your house isn't even running on the same voltages internally... most of the electronics nowadays use many voltage "rails": * 17-19v laptop chargers (the voltage has to be higher than the battery's voltage in order to charge the battery) * 12v for older hard drives * 5v for not quite so older hard drives and older logic * 3.3v for newer logic and newer hard drives * A veritable plethora of sub-3.3v rails for CPU chips and other high tech chips. * 120vDC for "universal" motors unless you replace all your appliance motors with 48vDC (or whatever) motors In addition, the current requirements of running at a non-lethal DC voltage inside your house would require much larger wire gauges than your current wiring in order to keep the resistive losses reasonable[2]. The rewiring costs would be staggering. [1] http://en.wikipedia.org/wiki/High-voltage_direct_current http://en.wikipedia.org/wiki/High-voltage_direct_current [2] Charts for 12v wiring, 48vDC would be 4x better, but still not good - http://www.westmarine.com/webapp/wcs/stores/servlet/WestAdvisorView?langId=-1&storeId=11151&catalogId=10001&page=Marine-Wire http://www.westmarine.com/webapp/wcs/stores/servlet/WestAdvi...

amalag 14y ago

I didn't follow why the article stated that AC is not ready for the grid of the future. This DC grid seems to be an incremental improvement, 10%? But IMO not a huge breakthrough.

specialist 14y ago

When I was a kid, Scientific American had a cover featuring a high voltage transistor, which was supposed to revolutionize power transmission. My very weak understanding is that energy transmission is directed by a delicate balancing of loads. Which is inefficient. Where using a solid state switching solution would be more efficient. Does this sound familiar to anyone?