Designing an off grid power plant

[Vicke]

Hello!

I have some plans that i want to share and get some feedback on before i start construction and buying parts. I have some land next to a lake that i can build a dam with head of 30m around 10000m2 and almost 50000m3.

I am thinking of solar panels and wind turbine to generate electricity to power pumps that fills the dam, then a 20kw generator driven by a pelton wheel is producing the electricity i will consume.
I'll use a computer to control the rpm of the generator by adjusting the jet flow to maintain 50hz, i will also have a diesel motor connected with one way bearings to the generator so i can start is and stop it while maintaining 50hz from the generator, i will also have a large flywheel on the same shaft with one way bearings and some clutch that make it start to spin slowly so i can power up the plant fast without waiting for the right rpm for too long.

My questions is how to make this most effective?
Im thinking of dc motors for the pumps, one per pump.
If i have max 600Vdc 30A from the solar panels i can have one 20kw dc pump directly connected to the panels at 50-100% power, and one 10kw ?V ?A at 25-50% power, and one 5kw ?V ?A for 0-25% power or even another smaller one. And the same setup for the wind turbine setup.

This setup at full consumption will use about 4m3 of water per minute maybe its possible to drive the generator directly from the pump motors via clutch or bearing when the usage and production is about the same to optimize efficiency.

I'm happy if anyone have some ideas on how to do this the best way and what motors, generators, panels, turbines and pumps i should use.
Thanks!

 

[rbelli1]

Wow! That's an ambitious project.

I would suggest first contracting with a civil engineer and a lawyer to see if this project is physically and legally possible. Starting something that big without fully understanding the risks sounds like a bad idea.

BoB

 

[Vicke]

Wow! That's an ambitious project.

I would suggest first contracting with a civil engineer and a lawyer to see if this project is physically and legally possible. Starting something that big without fully understanding the risks sounds like a bad idea.

BoB

Sounds like a good idea yes.
It is a big project but not as big as it sounds, where the dam will be is now a mountain with a V shape through it so just need to remove the trees and soil and make a wall in each end. And from one end there is a canyon like opening down to the lake where i can just put the pipes in and build the power house.
I want every detail before asking for permit to make it easier both to get it legal and in the process of building everything.

 

[anorlunda]

Wow! You have a lot of resources there, and a lot of ideas. To put it in perspective, you will have a DIY pumped storage hydro plant. Many people struggle with the problem of storage of solar and/or wind energy. You have the ideal set up.

I'm sure PF members can help with good suggestions. But first, let's clear the air about safety. Dangerous topics on PF are not allowed.

• Confirm that this system will not be connected to the power grid.
• Tell us more about your dam's structure. 30m is pretty high, and dam collapse is a serious risk.
• Assure us that you will clear your plans with the local authorities in terms of required permits, plans, and inspections.

 

[Vicke]

Wow! You have a lot of resources there, and a lot of ideas. To put it in perspective, you will have a DIY pumped storage hydro plant. Many people struggle with the problem of storage of solar and/or wind energy. You have the ideal set up.

I'm sure PF members can help with good suggestions. But first, let's clear the air about safety. Dangerous topics on PF are not allowed.

• Confirm that this system will not be connected to the power grid.
• Tell us more about your dam's structure. 30m is pretty high, and dam collapse is a serious risk.
• Assure us that you will clear your plans with the local authorities in terms of required permits, plans, and inspections.

This is in a are with no electricity so it will be a off grid system.

If one of the two dam walls collapses it will go straight down to the lake again witch will gain 0,04l/m2 if dam is full. I think i added a picture which shows the dam and the green line is where the water pipes will go. The green and red lines are the only two ways the water can go if it collapses, witch both ways is directly to the lake.

At the moment i am planning this in detail and then i will make a small scale with panels, pumps, water tank small generator and turbine and petrol engine and computer controlling the valve and test it in real conditions so i don't get stuck anywhere on the big project.

 

[jrmichler]

What country are you in? Do you own all the land for both high and low flooded areas? Before starting construction of a dam in the US, you would need a complete engineering study of the proposed dam. The study would include safety factors, worst case inflow (think 500 year rain event), and a complete analysis of a worst case dam failure. The dam hazard analysis needs to extend downstream to a point where a worst case dam failure would have negligible impact.

Dams, even small ones, need input from a qualified civil engineer. Did you know that a dam can fail on the upstream face if the upstream water level drops too fast?

I was involved in a dam hazard case a little over a year ago. The hazard analysis for a 2 meter high Earth dam showed that people living over a mile downstream were in a flood zone.

 

[anorlunda]

At the moment i am planning this in detail

It could be a fun design study.

But if you want to do it in real life, I'm sure that you will need permission from the authorities. They won't believe you that a dam collapse is not a hazard, they will demand that a civil engineer gives the opinions.

I suggest that you ask an engineer from Fortum (the local utility) for help.

 

[Vicke]

What country are you in? Do you own all the land for both high and low flooded areas? Before starting construction of a dam in the US, you would need a complete engineering study of the proposed dam. The study would include safety factors, worst case inflow (think 500 year rain event), and a complete analysis of a worst case dam failure. The dam hazard analysis needs to extend downstream to a point where a worst case dam failure would have negligible impact.

Dams, even small ones, need input from a qualified civil engineer. Did you know that a dam can fail on the upstream face if the upstream water level drops too fast?

I was involved in a dam hazard case a little over a year ago. The hazard analysis for a 2 meter high Earth dam showed that people living over a mile downstream were in a flood zone.

Okay i live on a island belonging to Finland, i own the land where the dam will be and around it and everything that might be flooded except the lake that it wil run into.
Some people are living close to the lake closest is 1km from where the dam can run out in the lake,
It would require a few meter wave before reaching their homes except a few boat houses that's on the water.
This dams displacement is 50000m3 and 30m over the lake and have little over 300 meter through woods until it reaches the lake so a big tsunami is not to expect, but a smaller wave is definitely going to happen.

The rain would average 0.5m a year in this area. And the dam is in the middle of the two natural water flows from the hill and will collect about 20000m2 of rain.

 

[anorlunda]

Some people are living close to the lake closest is 1km from where the dam can run out in the lake,
It would require a few meter wave before reachig their homes exept a few boat houses that's on the water.

What if the dam breaks in winter when the lake is frozen? Besides, what gives you the right to risk even a single boat house that does not belong to you.

As I said before, authorities won't accept your opinions, you need a professional engineer.

 

[Vicke]

What if the dam breaks in winter when the lake is frozen? Besides, what gives you the right to risk even a single boat house that does not belong to you.

As I said before, authorities won't accept your opinions, you need a professional engineer.

Yes of course. Just now in doing the math and want to figure out how good this will work in real and what i should use for components for the prototype and what results to expect.

Yes you are right but i will of course take all possible events in account before going to authorities and i will hire professionals for the construction plans.

I always take safety first but this post was more about the function of the generation of electricity and storage effectiveness, but if anyone have experience or ideas in construction of dams and safety regarding dams id like to know thanks.

 

[anorlunda]

OK, if you start with real numbers, you may find that the complication and expense of a dam isn't needed at all.

Start with your requirements. You're talking summer months only I suppose. At latitude 60, you have a lot of sun in summer, and almost zero in mid winter. I also guess that you need no heat, no air conditioning in the summer.

• What are your daily energy requirements kWh, and peak power requirements kW?
• How much will it cost for solar panels to produce that? (Wind? I have no idea how steadily the wind blows there.)
• Include the mechanism to rotate the panels to follow the sun through those 23 hour midsummer days.
• There must be other people in Finland with home solar projects. They can help you with the numbers.
• Next what is a reasonable cost to store that energy? A friend of mine at 45 degrees north uses two Tesla Powerwall batteries. The USA price for those is $13400. That is probably the simplest most reliable way to do it. So any storage scheme you think of, like a dam, much cost substantially less than that or else it is not justified.

That should get you started. Let us know when you have the numbers.

 

[Vicke]

OK, if you start with real numbers, you may find that the complication and expense of a dam isn't needed at all.

Start with your requirements. You're talking summer months only I suppose. At latitude 60, you have a lot of sun in summer, and almost zero in mid winter. I also guess that you need no heat, no air conditioning in the summer.

• What are your daily energy requirements kWh, and peak power requirements kW?
• How much will it cost for solar panels to produce that? (Wind? I have no idea how steadily the wind blows there.)
• Include the mechanism to rotate the panels to follow the sun through those 23 hour midsummer days.
• There must be other people in Finland with home solar projects. They can help you with the numbers.
• Next what is a reasonable cost to store that energy? A friend of mine at 45 degrees north uses two Tesla Powerwall batteries. The USA price for those is $13400. That is probably the simplest most reliable way to do it. So any storage scheme you think of, like a dam, much cost substantially less than that or else it is not justified.

That should get you started. Let us know when you have the numbers.

This is for year round use as long as i have liquid water, then i have diesel for backup.
Main heating is with wood so the scale of this setup is larger than needed but if no one is home for a few weeks the dam when full should be enough to produce 20kw for 10 days, and the generator is also over sized if just heating is on so it will last longer.
Requirement per day would be maximum 180kwh a day in the worst winter days.
As this setup should handle all power i can possibly use for heating and workshop and cooking at the same time 20kw should be max.

I live on a island and on top of a hill it is wind almost every day.
A wind turbine is more expensive to buy but is possible to build by my self, i can use a 10kw wind turbine that will probably generate about the same as the 20kw solar panels in a year.

To get the power grid to this area is a cost of around 38k€ plus electricity for around 2-4k€ per year, after 10 years i would have paid around 70k€ so if i spend less than that on this project i have made a profit after 10 years. Also batteries have a loss of power when stored and they have a lifetime so they must be replaced and charging is about the same loss as pumped storage.

If buying a lot of panels at the price can go below .5€/w this is 10k€ for 20kw of panels if i can directly connect them to the pump i won't need a inverter which is actually half the price of the pump. And generator is about same as pump.

The dam is not so expensive to build because i have the material and machines needed to transport material and remove the trees and soil that are there now.
The dam if built properly is a one time cost. And generators and motors hopefully only need bearing changes.

 

[rbelli1]

The dam if built properly is a one time cost.

Price the concrete that you will need to build the dams before starting. This will be a substantial part of the cost.

When you build the power system please add lots of instrumentation to record the performance. We would be very interested in the results.

BoB

 

[Vicke]

Price the concrete that you will need to build the dams before starting. This will be a substantial part of the cost.

When you build the power system please add lots of instrumentation to record the performance. We would be very interested in the results.

BoB

Yes that will cost a lot.
Yes i want to have and log as much measurements as possible also to spot problems and wear as soon as possible and figure out how to optimize with time and to calculate the efficiency at different loads and time of the year.

 

[anorlunda]

I repeat:

There must be other people in Finland with home solar projects. They can help you with the numbers.

 

[berkeman]

Thread closed for Moderation...

 

[anorlunda]

The mentors are very skeptical of this idea, but so far it does not violate any PF rules, so I will reopen it.

@Vicke we do not have enough data for good quality answers. Before proceeding, please provide us with two important numbers.

1. How many m² of panels would you need to provide 180 kWh of energy at mid-winter? What is the installed cost of solar panels in Finland?
2. What is the volume in m³ of this dam? What is the cost of concrete and rebar for that? Please show some sketches to explain your calculations.

Because of your high latitude, at mid-winter the sun is up only a few hours and does not rise high in the sky.

 

[Vicke]

The mentors are very skeptical of this idea, but so far it does not violate any PF rules, so I will reopen it.

@Vicke we do not have enough data for good quality answers. Before proceeding, please provide us with two important numbers.

1. How many m² of panels would you need to provide 180 kWh of energy at mid-winter? What is the installed cost of solar panels in Finland?
2. What is the volume in m³ of this dam? What is the cost of concrete and rebar for that? Please show some sketches to explain your calculations.

Because of your high latitude, at mid-winter the sun is up only a few hours and does not rise high in the sky.

Okay thank you!
I was planning on 130m2 panels which will give about 60kwh a day in winter.
The spot i have planned for the panels is on a hill with almost nothing covering the sun from reaching them eaven the few hours in winter.

I was thinking og minimum 10kw wind turbine which will generate on about 60kwh a day in winter.

The dam should be full when the worst months come and that will last for 60 days together with the wind and solar power, and if that runs out or the dam frezes to much i can run the diesel engine until the ice melts again.

The dam shuld require a maximum of 200m3 of concrete which is about 100€/m3 and the rocks and gravel i have on the place.

The cost for the panels is quite high here but i can order for a total of 10000€.

The wind turbine I am not sure of the the price i might build a vertical turbine by my self.

I can upload some sketches soon.