Hawaii Halves Solar Incentives After Overwhelming Response

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Hawaii is well on its way to meeting its state renewable energy goal of obtaining 40% of its power from locally generated renewable sources by 2030. The Big Island already gets nearly half of its power (44%) of its electricity from renewables, and experts think it could be completely powered by renewables by 2020. But for some, there is a downside to all this development, most of which is solar. The Los Angeles Times interviewed Hawaiian...

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nsaspook

Re: Hawaii Halves Solar Incentives After Overwhelming Response

The original LA times piece: http://www.latimes.com/news/nationworld/nation/la-na-hawaii-solar-20121118,0,595680.story

Hawaiian Electric Co. on Oahu, which oversees subsidiary utilities on Maui and the Big Island, has warned that the explosion of do-it-yourself solar could threaten parts of the power grid with the possibility of power fluctuations or sporadic blackouts as the power generated by homeowners — unpredictable and subject to sudden swings — exceeded output from power plants in some areas.

So rapid is the growth that Hawaiian Electric at one point proposed a moratorium on solar installations, a plan that met with immediate outrage and was quickly withdrawn. But utilities are requiring expensive "interconnection" studies, such as the one the Lees had to do, in solar-saturated areas to analyze what impact a new unit is going to have on the utility system before it can connect to the grid.

rollandelliott

Re: Hawaii Halves Solar Incentives After Overwhelming Response

44% from renewables that is amazing! wish every state was like that.

Rick1

Re: Hawaii Halves Solar Incentives After Overwhelming Response

rollandelliott wrote: »

44% from renewables that is amazing! wish every state was like that.

Every state would be if their utility companies charged 36 to 40 cents per KWH like Hawaii.

ggunn

Re: Hawaii Halves Solar Incentives After Overwhelming Response

rollandelliott wrote: »

44% from renewables that is amazing! wish every state was like that.

It's not without its problems. I don't know the grid structure out there - does each island have its own autonomous grid or are they connected by undersea cables? Even assuming they are interconnected, though, it's still a very small grid compared to anything on the mainland, and the more solar is on the grid, relatively speaking, the more problematic grid stabilization becomes, since grid tied solar inverters are current sources and produce what they produce irrespective of demand. To keep the line voltage stabilized, grid administrators must allocate generation resources much more dynamically than they would if solar were a smaller component of the overall picture.

When I was out at SPI, I talked for a bit with a grid administrator from Puerto Rico. This has become a big problem for them since (I believe) the Air Force installed a very large grid tied PV system on base. Their out of date control structure is having major problems with grid stabilization; voltage fluctuations plague them.

inetdog

Re: Hawaii Halves Solar Incentives After Overwhelming Response

ggunn wrote: »

When I was out at SPI, I talked for a bit with a grid administrator from Puerto Rico. This has become a big problem for them since (I believe) the Air Force installed a very large grid tied PV system on base. Their out of date control structure is having major problems with grid stabilization; voltage fluctuations plague them.

I corresponded with a poster from Puerto Rico who mentioned the problems he was having with his home GTI inverter losing sync when the grid fluctuated too far. He was on the same POCO distribution segment as the Coast Guard base. During the night his 240 volt nominal was ~230 volts, and when the sun was shining full on the base during midday his 240 was 260 or higher and his GTI inverter cut off.
The real smoking gun behavior was that during the day when a cloud passed over the base his lights would dim and his motors would slow down and/or draw more current. And the voltage would even go below 230 during those events because of the continuing daytime load from the base itself.
There just was not enough elasticity in the grid to handle that much of a load/supply fluctuation, and there did not appear to be any POCO tap-changers or other regulators which could correct the voltage, even slowly. And the POCO did not give him any hope for a quick solution.

The situation in Hawaii may be better in terms of network stabilization, but unless they put in some really large energy storage (like sodium-sulfur batteries, etc.) they will be hard pressed to deal with the short term output fluctuations. Trying to regulate demand through a deliberate brownout is just not a good position to be in. If they have enough commercial interruptible loads (like AC) it might help, but making heavy use of that would probably drive commercial users off the plan.

vtmaps

Re: Hawaii Halves Solar Incentives After Overwhelming Response

inetdog wrote: »

I corresponded with a poster from Puerto Rico who mentioned the problems he was having with his home GTI inverter losing sync when the grid fluctuated too far. He was on the same POCO distribution segment as the Coast Guard base.

For those interested, more here:
http://forum.solar-electric.com/showthread.php?16478

--vtMaps

stephendv

Re: Hawaii Halves Solar Incentives After Overwhelming Response

I mentioned this in another thread... they have similar problems in germany with so much PV online, so they're created a new law whereby all new grid tie inverters must be able to vary their output based on grid frequency (similar to what the sunny boy's do in off-grid mode). So grid operators would have some control of grid connected solar. http://www.vde.com/en/fnn/pages/50-2-hz.aspx

ggunn

Re: Hawaii Halves Solar Incentives After Overwhelming Response

inetdog wrote: »

I corresponded with a poster from Puerto Rico who mentioned the problems he was having with his home GTI inverter losing sync when the grid fluctuated too far. He was on the same POCO distribution segment as the Coast Guard base. During the night his 240 volt nominal was ~230 volts, and when the sun was shining full on the base during midday his 240 was 260 or higher and his GTI inverter cut off.

That must be the same system the guy I talked to was telling me about. Coast Guard, not Air Force. Once again, storage (lack of it) is the Achilles' Heel of renewable energy.

inetdog

Re: Hawaii Halves Solar Incentives After Overwhelming Response

stephendv wrote: »

I mentioned this in another thread... they have similar problems in germany with so much PV online, so they're created a new law whereby all new grid tie inverters must be able to vary their output based on grid frequency (similar to what the sunny boy's do in off-grid mode). So grid operators would have some control of grid connected solar. http://www.vde.com/en/fnn/pages/50-2-hz.aspx

This is a luxury feature which is possible in Germany because it is not part of a larger AC-only intertie and thus can play games with system frequency, going as high as 50.5 Hz on a short term basis.
Trying to do that in the US would not be possible. Instead, some kind of out-of-band communication via Internet or Power Line Carrier data transmission would be needed. Fortunately (or unfortunately) the US (North America) is not near that fraction of generation capacity being solar PV yet.

nsaspook

Re: Hawaii Halves Solar Incentives After Overwhelming Response

Most of the studies and research I've read says the most the overall US electrical grid (designed for high inertia) can handle is about 10% RE power before we start to have serious grid frequency stability caused by the lack of energy storage needed to emulate the inertia created from the stored kinetic power in large rotational generators.

http://www.sandia.gov/eesat/2011/papers/Lim_EESAT11_Paper.pdf
https://lirias.kuleuven.be/bitstream/123456789/345286/1/Grid_Inertia_and_Frequency_Control_in_Power_Systems_with_High_Penetration_of_Renewables.pdf

inetdog

Re: Hawaii Halves Solar Incentives After Overwhelming Response

nsaspook wrote: »

Most of the studies and research I've read says the most the overall US electrical grid (designed for high inertia) can handle is about 10% RE power before we start to have serious grid frequency stability caused by the lack of energy storage needed to emulate the inertia created from the stored kinetic power in large rotational generators.

http://www.sandia.gov/eesat/2011/papers/Lim_EESAT11_Paper.pdf
https://lirias.kuleuven.be/bitstream/123456789/345286/1/Grid_Inertia_and_Frequency_Control_in_Power_Systems_with_High_Penetration_of_Renewables.pdf

I have managed to convince myself that I understand what you so tersely summarized, and therefore I agree. I will read the cited papers for the details. :-)

I find interesting the proposal in the second paper that RE sources such as wind (or hydro) could contribute to short term stabilization by operating past their maximum continuous power output (slowing down the rotating parts to extract energy) while getting the same amount of control from PV without energy storage would require operating them at less than full capacity most of the time. In the direction of excessive generation in the grid (sudden load drops), both could easily be made to respond by dropping their output.
And whatever else is done, no single large-scale RE system should be switched on or off the grid abruptly.

nsaspook

Re: Hawaii Halves Solar Incentives After Overwhelming Response

I have a feeling that reducing output (and reducing money) won't be a very popular solution. The DOE just started a 5 year $120 million program to improve storage but most companies already know there's a trillion dollars in business if they can crack the problems of it being stable, low-cost and high density. I just hope somebody finds the answer.
http://www.anl.gov/articles/department-energy-awards-120-million-battery-hub-argonne-led-group

inetdog

Re: Hawaii Halves Solar Incentives After Overwhelming Response

nsaspook wrote: »

I have a feeling that reducing output (and reducing money) won't be a very popular solution.

You would have to pay them to do it, of course. Or make it a government mandate, either way delaying true RE parity for the corresponding length of time instead.

ggunn

Re: Hawaii Halves Solar Incentives After Overwhelming Response

inetdog wrote: »

And whatever else is done, no single large-scale RE system should be switched on or off the grid abruptly.

Easier said than done. Wind and solar are subject to the whims of the weather, which can change abruptly here in Texas.

nsaspook

Re: Hawaii Halves Solar Incentives After Overwhelming Response

It's a good sign of progress in RE sources that we are now past the first stage of just making hardware cheap and are now working on what it takes to make it work with the current grid infrastructure. It looks like the key to making the grid smarter is to make decentralized RE energy sources act as a dumb, fat and slow generator.

The problem in this region is too much power generation, no way to save it and no place to send it.
http://www.ect.coop/public-policy-watch/energy-environment/northwest-hydroelectricity-wind-power-report/41577
http://www.bpa.gov/news/pubs/FactSheets/fs-201205-working-together-to-address-northwest-oversupply-of-power.pdf

Attachment not found.

ggunn

Re: Hawaii Halves Solar Incentives After Overwhelming Response

nsaspook wrote: »

It's a good sign of progress in RE sources that we are now past the first stage of just making hardware cheap and are now working on what it takes to make it work with the current grid infrastructure. It looks like the key to making the grid smarter is to make decentralized RE energy sources act as a dumb, fat and slow generator.

It's kinda like in Animal House at the hoity toity rush party where every time an undesireable pledge candidate ventures from the loser's room he is handed off from one frat guy to another and soon finds himself right back where he started. Most problems with incorporating large scale renewable energy come back to the same issue.

In a word - storage. With enough onsite storage, a PV array can behave as a voltage source rather than a current source and supply current on demand as well as supply power steady state when clouds come over. Wind is in a similar position. Without utility scale storage, renewable energy can never supply a very large portion of the grid's needs.

inetdog

Re: Hawaii Halves Solar Incentives After Overwhelming Response

ggunn wrote: »

Easier said than done. Wind and solar are subject to the whims of the weather, which can change abruptly here in Texas.

I was thinking more of planned out-of-service conditions. For a large enough area covered, a wind or solar plant should go in and out of power production over a timespan of several seconds at least, and will not be producing near full power when at the transition. But it would be possible to hit the panic button while the system was at full power, and that event could be a big strain on the grid.
Slow start, slow stop should be part of the control system for manual operation.
For really gusty winds that change direction rapidly, if that is what you have down there, yes, you could catch the whole wind farm running at full output then suddenly facing in the wrong direction for as long as it takes for them to rotate. There would be some capacity to do a gradual output reduction by using the mechanical inertia of the system (one of the reference articles stated 3-5 seconds critical time, comparable to the inertia factor for a lot conventional power plants.) But the controller/inverter might have to be specifically designed to do this.

ggunn

Re: Hawaii Halves Solar Incentives After Overwhelming Response

inetdog wrote: »

I was thinking more of planned out-of-service conditions. For a large enough area covered, a wind or solar plant should go in and out of power production over a timespan of several seconds at least, and will not be producing near full power when at the transition. But it would be possible to hit the panic button while the system was at full power, and that event could be a big strain on the grid.
Slow start, slow stop should be part of the control system for manual operation.
For really gusty winds that change direction rapidly, if that is what you have down there, yes, you could catch the whole wind farm running at full output then suddenly facing in the wrong direction for as long as it takes for them to rotate. There would be some capacity to do a gradual output reduction by using the mechanical inertia of the system (one of the reference articles stated 3-5 seconds critical time, comparable to the inertia factor for a lot conventional power plants.) But the controller/inverter might have to be specifically designed to do this.

A solar inverter's output varies as does the sunlight striking the array, which is a gradual process, but unless there are multiple inverters which can be shut down individually, I don't know of a way to shut down a PV system gradually without utilizing (here we go again) some form of energy storage.

inetdog

Re: Hawaii Halves Solar Incentives After Overwhelming Response

ggunn wrote: »

but unless there are multiple inverters which can be shut down individually, I don't know of a way to shut down a PV system gradually without utilizing (here we go again) some form of energy storage.

Maybe commercial-scale GTIs should be required to incorporate a soft-shutdown circuit? No energy storage needed, and could probably be done within the existing MPPT circuitry.

nsaspook

Re: Hawaii Halves Solar Incentives After Overwhelming Response

inetdog wrote: »

Maybe commercial-scale GTIs should be required to incorporate a soft-shutdown circuit? No energy storage needed, and could probably be done within the existing MPPT circuitry.

How can you have a "soft-shutdown' of PV energy with no energy storage? If it's pure grid-tie the reactive energy stored in a transformer or commutation capacitors might give you a few milliseconds but that's all.

inetdog

Re: Hawaii Halves Solar Incentives After Overwhelming Response

nsaspook wrote: »

How can you have a "soft-shutdown' of PV energy with no energy storage? If it's pure grid-tie the reactive energy stored in a transformer or commutation capacitors might give you a few milliseconds but that's all.

Soft shutdown without energy storage == reduce the power drawn from the panels slowly over whatever time period is determined to be appropriate, without messing with the grid-facing side of the GTI. The solar panels are not going to mind that, and an MPPT controller could easily be programmed to do that.

Agreed that if you are talking about a soft-shutdown when a cloud passes in front of the sun or somebody chops the array cable with a fire axe, that is whole different order of magnitude problem. But that is not what I was suggesting.

nsaspook

Re: Hawaii Halves Solar Incentives After Overwhelming Response

inetdog wrote: »

Soft shutdown without energy storage == reduce the power drawn from the panels slowly over whatever time period is determined to be appropriate, without messing with the grid-facing side of the GTI. The solar panels are not going to mind that, and an MPPT controller could easily be programmed to do that.

For planned maintenance actions it would be useful but I would think that power ramp control is a standard option for a large utility grade PV inverter. Under normal PV operational conditions the time variable of energy variations is an unknown set of ramp rates up or down. If the requirement is pure MPPT inverter ramp rates are usually fast to match the PV ramp rates. On a inertia-less solar energy system the ramp-up rate can be controlled to emulate inertia by leaving a buffer of extra power from the upper MPPT level to the lower level output set-point but that ramp rate is controlled by the instantaneous power level on the panels once that input level goes below the current inverter output power set-point. In a PV storage-less system with emulated inertia from reduced power, MPPT becomes secondary and the prediction of what the output level should be becomes the major problem during times of rapidly changing light conditions and low reserve base-power. Even a small about of storage allows systems to run at close to MPPT again under most conditions when other sources of power are idled.

http://wpweb2.tepper.cmu.edu/ceic/pdfs/ceic_07_05_lvu.pdf
http://energy.sandia.gov/wp/wp-content/gallery/uploads/093669c.pdf

A very good study about the effects of adding storage to large scale PV systems. http://rael.berkeley.edu/sites/default/files/Solomon%202011-%20Appropriate%20storage%20for%20high-penetration%20grid-connected%20photovoltaic%20plants.pdf