3kW Grid Tied Solar PV: Watts and Warts.

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#1084312 8-Jul-2014 19:22

Ok, think I've read the whole thread now, and am interested to see if anyone has experience or ideas on a part microhydroelectric system.

I have access to a stream which would generate 280w continuously 24hrs... To equate to a solar panel install, how much kWh/day is this... 24x280=6,720... Is this then a 6kWh equivalent?
How do I calculate batteries when output is so low, but 100% solid...

wellygary

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#1084330 8-Jul-2014 19:42

It's more efficient to store the water than the electricity,

Ideally , build a small dam and install a couple of kilowatt generator, then you can run the plant to match your load.

PhantomNVD

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#1084377 8-Jul-2014 20:30

AFAIK I'd need the battery bank to service a load greater than the <300w output, but as it runs 24/7 I should easily be able to replace this overnight and through the day when away and only running my base load?

Also, I only have 40m of the stream passing through my backyard and a 2m head, so dam would be

a)unlikely to be feasible, and
B) not really useful unless the head raised considerably to facilitate a higher power output?

So what size battery bank will I need to 'store' the capacity required for peak n
(Evening) use please?

Parewanui

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#1084391 8-Jul-2014 20:44

PhantomNVD: AFAIK I'd need the battery bank to service a load greater than the
Also, I only have 40m of the stream passing through my backyard and a 2m head, so dam would be

a)unlikely to be feasible, and
B) not really useful unless the head raised considerably to facilitate a higher power output?

So what size battery bank will I need to 'store' the capacity required for peak n
(Evening) use please?

It's a long discussion, and you could try reading the information from these experts.
http://www.powerspout.com/turgo/
They are the biggest micro-hydro in NZ, maybe even APAC.
Over 20 years experience.
Good youtube demos.
Case studies.
1000's of customers.
3 different micro-generators with the latest covering a large head range.

raytaylor

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#1084413 8-Jul-2014 20:59

mattwnz: Anyone got one of those ones being advertised on TV for about 7 grand. Although I see in the fine print that it appears to be 1.5kW, so appear to be half the generation capacity.

I am wondering if it isn't better to centrally generate all power, rather than each house having some generation capacity. There is potentially better economies of scale in this, and all maintained is centrally done.

I know a subdivision developer in waipukarau who is splitting his property into 5 sections.
He is planning to have a central solar co-op at the rear of the subdivision with probably a 15kw solar array. However he then has to transport that power to the houses, and encourage the homeowners to use it during the day, otherwise they have to export it back to the grid and loose out on its full value.

I personally believe that every council in the country should now be requiring

All New Homes
- North Facing Roof slope suitable for solar to be added in the future
- At least 1x heat pump

All New Homes bigger than a granny flat
- Heat pump hot water cylinder if gas is not connected to a califont

All New Homes 4 bedrooms or bigger
- Minimum of a 2kw solar installation

Germany (which doesnt have huge amounts of sun) is now the biggest solar sourced energy producer in the world because they provided rebates and tax breaks to encourage homeowners to install solar systems.
I believe we can do it just by encouraging common sense - since the requirements I list above do indeed make financial sense and are not hugely costly when building a new home or flat.

Ray Taylor

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PhantomNVD

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#1084416 8-Jul-2014 21:03

@Parewanui Thanks, the powerspout company is where I did the math on what it would produce, (using their LHs genny) looks awesome, but I have yet to find an online calculator for hydroelectric battery requirements.. Is it just take a good guess ands add as necessary?

Parewanui

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#1084420 8-Jul-2014 21:11

PhantomNVD: @Parewanui Thanks, the powerspout company is where I did the math on what it would produce, (using their LHs genny) looks awesome, but I have yet to find an online calculator for hydroelectric battery requirements.. Is it just take a good guess ands add as necessary?

No guessing.
If there is not a case study on their website that fits your requirements, then ask them for advice.
If it is a lot of advice them they will want to charge you an hourly rate.
E.g. this is their original business (sister company)...
https://www.ecoinnovation.co.nz/
They sell batteries off-grid systems, etc...
They will know want your options are.

richms

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#1084450 8-Jul-2014 22:04

raytaylor:
I personally believe that every council in the country should now be requiring

All New Homes
- North Facing Roof slope suitable for solar to be added in the future
- At least 1x heat pump All New Homes bigger than a granny flat
- Heat pump hot water cylinder if gas is not connected to a califont

All New Homes 4 bedrooms or bigger
- Minimum of a 2kw solar installation

Germany (which doesnt have huge amounts of sun) is now the biggest solar sourced energy producer in the world because they provided rebates and tax breaks to encourage homeowners to install solar systems.
I believe we can do it just by encouraging common sense - since the requirements I list above do indeed make financial sense and are not hugely costly when building a new home or flat.

Tax breaks and rebates just serve to keep the prices high and stop innovation. look at the ripoff that was the subsidized insulation. No way do I want to see rebates on this sort of gear. The rebate comes in the form of lower energy costs.

I would rather see the council get the costs of building down to help with the insanely high prices of it rather than adding even more comliance costs for even the most basic of renovations. They could do that by stopping with all the inspections and requirements for concents for so many things.

Richard rich.ms

raytaylor

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#1084456 8-Jul-2014 22:14

PhantomNVD: AFAIK I'd need the battery bank to service a load greater than the
Also, I only have 40m of the stream passing through my backyard and a 2m head, so dam would be

a)unlikely to be feasible, and
B) not really useful unless the head raised considerably to facilitate a higher power output?

So what size battery bank will I need to 'store' the capacity required for peak n
(Evening) use please?

280 watts continuous is 6.7kwh of power a day
A 2kw solar system will provide 2.5kwh to 15kwh of power a day

As stated above, it is cheaper to store the water, than to buy batteries.

It is 10pm right now
We have the heat pump running, tv's computers etc

We are using 2.57kwh or 66 cents per hour at 26c per unit

So to supply that amount of power for say 8 hours with only a 10% drop in battery capacity so hopefully they will last 2 years
(shallower overnight discharges = longer lasting batteries, deeper discharges mean you need to replace them sooner)
would mean we need
2.6kwh x 1000 to get watts = 2600 watts
2600 watts x 8 hours = 20,800 watts

To budget that 20,800 watts is only 10% of total storage capacity, we multiply 20,800 x 10 to find the 100% figure
= 208,000 watts

If we store our power in large 2 volt batteries we can divide the 208,000 watts by 2 volts to get amp hours which is what batteries are rated for
208,000 / 12 = 17,333 ah

Looking at pricing on our battery suppliers website for a 12v 17,333ah battery array, the best price I can find is
$679 for a 325ah 12volt cell
So 17,333ah / 325ah = 54 batteries

$36k for 54 x 12volt batteries.

$36 thousand dollars is a bit much.
Hence why it is much cheaper to store the water, or grid tie and sell power to the grid, then buy it back when you need it.

You can also cut that down by a factor of 5 if you go and use a wood burner and wetback to heat your water. But replacing the batteries is still not worth the extra expense.

In the UK they have systems where during the night off-peak when power is cheap, they pump a lake worth of water up a hill, then when the 6pm pickup occurs, they flush a lake worth of water down a mountain through a dam to run generators which supply the extra peak load, and the company running the system is able to sell the power back at a higher on-peak rate.

The fact that solar panels have dropped in price over the last 5 years means hydro and even heating your water by evacuated tube is just way more expensive unless done on large scale.

5 years ago I was paying $1200 for a 120 watt panel.
Last week I ordered a pallet of 120 watt panels for almost $150 each.
The price of batteries has stayed exactly the same.

Why spend money on batteries when you can just buy a bunch of extra solar panels, oversize your requirements and sell back to the grid more than what you use and still break even without the cost of the batteries.

Edit - you got me thinking about the numbers now:
So lets say we were to not buy batteries, and instead buy solar panels
Lets also assume that you have a wood burner so the battery capacity only needs to be 1/5th of what I estimated above.
This is still a $7k spend.
Then lets say we used 290 watt panels, which cost $420 including $50 in that price for mounting each one.

$7000 / $420 = 16 panels
16 x 290watts = 4.6kw

On a sunny day, a 4.6kw solar array will capture 27kw over 6 hours , or 5kw on a cloudy day.

According to http://www.napier.climatemps.com/ napier has a 47% chance that any given daylight hour will be sunny even in our worst month. So we could say that over 30 days, we could expect 84 hours of sun, 96 hours of cloud or rain
4.6kw x 84hours = 386.4kw
(4.6kw x 20% cloudy efficiency) x 88.3kw

Sun + Cloud
386kw + 88kw = 474kw total captured in winter

474kw is less than half our consumption (1,138kw units last month)

So if i wanted to cover our power bill completely, I would need to triple the size of the solar array, or get my flatmates to turn stuff off when they are not using them.
But if I could use all that power directly, it would cause a $99.50 drop in our power bill each month.
Add $3k for inverter and net meter swap over, I could be looking at total cost of setup of $10k and payback of 8.3 years

Result
I have a flatmate who runs an oil heater in their bedroom on max for 6+ hours a night for half the year
I think i might just get another heat pump for the other end of the house which will eliminate an oil heater saving 327 kw or $72 per month. A $1k heat pump will have a pay back within 24 months and is much better spent.
After that I would look into a heat pump hot water cylinder
It all seems much better than the cost of switching straight away as this stuff needs to be put in place first otherwise the solar savings arent going to work out.
And a little 300 watt hydro unit definitley wouldnt be able to capture enough energy in 24 hours to satisfy the household demand - even if there was a huge battery bank to store the power - it just wouldnt get replenished fast enough.

Ray Taylor

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richms

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#1084461 8-Jul-2014 22:20

raytaylor:
5 years ago I was paying $1200 for a 120 watt panel.
Last week I ordered a pallet of 120 watt panels for almost $150 each.
The price of batteries has stayed exactly the same.

Why spend money on batteries when you can just buy a bunch of extra solar panels, oversize your requirements and sell back to the grid more than what you use and still break even without the cost of the batteries.

Because its not financially sustainable for the power companies to be charging in the arcane way that they are where a peak time evening kWh costs the same as a day time noone at home kWh does, so the value of the daytime kWh in residential areas will drop to near nothing, as the grid isnt made to transport it to industrial areas where it can be used, so you will have all this unused capacity on your roof and end up getting paid a pittance for it if you can even sell it, and then the evening load will have to be charged at a much higher rate to allow for the fact that it is all coming from really expensive power plants.

Whenever lines companies in other countries start to want an interconnect cost people get all up in arms about it slowing the uptake of solar. The reaility is that if they want to be able to push watts across a city to the factories that can actually use them, there is a real cost to it. Otherwise all your grid tie inverters will just keep going offline as the local grid voltage exceeds the cutoff threshold.

The way we pay for power will have to change to support the use of solar, if it doesnt then the people without panels are just propping up those that are able to get the investment together to get them installed.

Richard rich.ms

raytaylor

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#1084500 8-Jul-2014 23:55

Your right there.
Germany generates over 50% of its power from renewable energy now. Which is a pretty big achievement when nuclear is so cheap per MW for government budgets.

I believe that if we had solar on more and more homes, then the dependency on coal and gas at Huntley can be reduced, and perhaps even reduce the daytime hydro consumption which can be saved more for evenings and "a rainy day"

I hope to see Huntley demolished without being replaced in my lifetime

I would switch to solar myself at home if I could - have spent days researching it before I found we dont have a north facing roof
Hence why I believe any new build should at least have a north facing roof purely for the capability for it to be added later - and the instant benefit of more sunlight through windows. Our north facing wall goes into a garage between our two granny flats

Ray Taylor

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k1wi

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#1084518 9-Jul-2014 04:39

raytaylor: Your right there.
Germany generates over 50% of its power from renewable energy now.

That is incorrect. Germany's renewable electricity proportion is around 30% of total electricity, with 35% the Energiewende goal for 2020 and 50% the 2030 goal. Half of its renewable energy comes from solar and wind. For very brief periods Germany has produced 50% of its electrical demand through solar, however, this has been sunny weekend days in summer, when demand is particularly low. That figure is very low compared to New Zealand's 70-75% figure, thanks to hydro.

raytaylor: I believe that if we had solar on more and more homes, then the dependency on coal and gas at Huntley can be reduced, and perhaps even reduce the daytime hydro consumption which can be saved more for evenings and "a rainy day"

I hope to see Huntley demolished without being replaced in my lifetime

Huntly will continue to have a long term strategic role in New Zealand's energy reliability. The issue with New Zealand's energy demand is that it is very seasonal, not just variable across the day. Solar output is largely (but not completely) shaped with when New Zealand's hydro production is at its greatest and fossil fuel consumption is at its lowest - during summer. With minimal growth in hydro production (and very limited storage), there will need to be major investment in solar and wind before fossil fuel power stations are shutdown and demolished, especially if electricity demand picks up with the rebounding post-GFC economy [notwithstanding changes to consumption at Tiwai Point].

I don't disagree that New Zealand needs to move away from fossil fuels, but it should be done without subsidies or compulsion, but because the whole-of-life economics stack up, while maintaining New Zealand's security of supply. The economics of wind better suit New Zealand's energy demands.

Porboynz

110 posts

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#1084531 9-Jul-2014 07:31

PhantomNVD: Ok, think I've read the whole thread now, and am interested to see if anyone has experience or ideas on a part microhydroelectric system.

I have access to a stream which would generate 280w continuously 24hrs... To equate to a solar panel install, how much kWh/day is this... 24x280=6,720... Is this then a 6kWh equivalent?
How do I calculate batteries when output is so low, but 100% solid...

280W would not even cover my homes base load of 500W. However it's still a fun project generating your own power and it could be used to heat your hot water or run a freezer etc. I suggest you get a power monitoring unit and start mapping out where your usage is and when it's being used as the first step in generating your own power, be it hydro or solar. Lots of solid advice in the posts above to consider. I concur with what Ray Taylor and k1wi advise and Parewanui is passionate about hydro.

PhantomNVD

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#1084587 9-Jul-2014 10:29

Thanks for all the insights!

Couple points to consider though..

I already run a very energy efficient home. Wood burner (free wood) and gas califont and oven/hob ($50-70/month depending on wife's baking)

Powers hop tells me I use 5kW/day summer, and 14 in winter, so 6kW/day is all my use in summer and nearly half in winter.
My base load then IS nearly 300W, so I'd definitely need some panels to perk up the battery bank for winter use, though that's also when they're least productive :(

It looks to be $22000 to connect to 'the grid' after "development costs" so the battery bank <15000 is equivalent already?

At 300W/h 24h/day I'd still cut my power bill in less than half annually, and pay off the micro hydro investment in a medium timeframe... even if I got $0 payback from the grid, so perhaps grid connected is simply a choice between battery bank vs grid use?

As I see it then (in my case) for such a small system, if I worked out how to run the base load directly from the hydro, the grid would just be factored against 'solar and battery' use at peak, vs grid fees, especially if grid connect >= solar install

nutbugs

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#1084613 9-Jul-2014 11:11

@PhantomNVD. A couple of comments about my experiences. (I probably should create a new thread about all this as someone suggested a while back - time is short and the todo list is long! It is on it though :))

We elected to install a second turbine and reduce the battery bank capacity so that we could cover a larger base load. We have plenty of flow rate in our stream so this wasn't an issue - simply installed a larger size pipe. We actually have capacity in the feed pipe to run three turbines. The excess generation is dumped into a hot water cylinder so we can have lots of outdoor hot baths :)

As per PM's - I will dig out our logic for battery bank sizing etc and get that to you.

The batteries are the weakest link overall when you consider the maintenance and cost. We are 6 or 7Km from the nearest grid point across unfriendly terrain so a grid tie is not an option. If it was - I think I would go that way. The downside obviously is that if the grid is down so is your alternative power! Not sure how they manage the Hydro connections - it will need a load somewhere I think?

We have 16 x 6v 225AHr batteries.
We are running 48v - so that is two banks of 8.

We really wanted to cover peaks above 1KW or so - of which there are not many - we keep everything very efficient - and a few hours outage. This has seemed to work well enough so far.

I will dig out some more info and see what else I can share :)

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