# Solar power in and out



## baobao (May 7, 2019)

Can someone please explain to me some ins and out of solar power production in EDP.

I understand effectively that; EDP pays effectively zero for any power not used.

However I want to understadn how it calculated power produced.

So if i have solar power installed and connected to edp. Lets say during daylight I am producing energy and i am using it up. Howver is it as simple as stating - between 9am and 9.15 am you produced X and you used Y - so you you should pay Y- X?

i cant find anywhere such details obviously lack of portuguese being probably my biggest obstacle.


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## Strontium (Sep 16, 2015)

The usual way is the power supplied meter (ie the electricity you get billed for) only registers the power going from the grid into your property.
If you produce more solar electricity then the electricity you are using the meter does not register anything as there is no power supplied from the grid.


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## Heyo307 (Dec 26, 2019)

Hi!


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## John and Cecil (Dec 22, 2019)

I too am interested in your question, thank you.

I know in the USA, or at least parts of the USA, it is possible to connect a solar array to the grid and not only use your own generated electricity but to sell the excess electricity you create back to the electrical supplier. I guess this is not the case in Portugal?


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## John and Cecil (Dec 22, 2019)

I have been considering going off grid before we moved here and I had another idea (if power cannot be sold to the utility provider). I was thinking about disconnecting from the electrical grid entirely and installing an array of solar panels connected to a small battery that could handle powering the home for at least a few hours while the main storage battery was not connected to the system. The main storage battery would be an electric car like the Nissan Leaf which now comes with a 60kwh battery which is good for 200+ miles. At my last home 60kwh could power my home for at least a week. This way the car itself is charged by the solar panels, and it would be best to drive the car at night or during the day when the charge is already full. When not being driven the car is connected to the solar panels and the car is wired so that the car battery is also powering the home. When the car is being driven the home would draw power from the panels and from the small secondary battery. Obviously this would not be a good setup for commuters (unless their work has solar panels and allows them to charge their battery while at work).


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## smudges (May 2, 2013)

I'm looking to buy a house with solar or get it put in. I'm waiting for the battery technology and lifespan/recyclability etc to be improved then I'll get a hybrid and charge it from the solar system.
That's the plan, anyway!
John and Cecil - a very Happy New Year to both of you, may 2020 bring you closer to where you're aiming to be.


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## JohnBoy (Oct 25, 2009)

John and Cecil said:


> I too am interested in your question, thank you.
> 
> I know in the USA, or at least parts of the USA, it is possible to connect a solar array to the grid and not only use your own generated electricity but to sell the excess electricity you create back to the electrical supplier. I guess this is not the case in Portugal?


I'm not sure how much the electrical supplier will pay for your excess power John, but when I last checked it was very little. As if that wasn't bad enough, the government look on it as a business and tax you accordingly. I must stress, that was the last time that I enquired, possibly four years ago now so it might have changed.


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## John and Cecil (Dec 22, 2019)

Yes, they do not pay very much. I believe that you can use the credits to offset your nightly electricity usage so you don't really make a profit though, in the USA anyway. 

The problem with not being able to supply power to the grid means you need batteries in your solar system, and batteries are expensive and can be dangerous. But there are ways to cut your electricity usage if you disconnect from the grid completely. I have read that converting a top loading ice chest into a refrigerator (modifying the thermostat) uses significantly less energy than a standard upright model (a large chest freezer used as a fridge uses maybe 250wh per day). Also using high efficiency led cobs and under-powering them for lighting can use significantly less power for lighting (250 lumens per watt). Perhaps run a high efficiency led projector for entertainment along with an efficient laptop computer, and use gas for cooking/heating. Perhaps it is possible to get down to 2kwh of energy consumption per day. Then you can run everything off a 4kwh battery, and you could have 2 batteries which would also power a small electric motorcycle. You could probably build your own 4kwh li-ion batteries for maybe $1500 each. While you are out riding the motorcycle the other battery would be charging and powering the home. You would not need too many solar panels for this setup and it would eliminate your need to buy both electricity and gasoline.


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## JohnBoy (Oct 25, 2009)

Wow! You have certainly gone deeply into this and I cannot wait to read Strontium's response to your ideas.


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## John and Cecil (Dec 22, 2019)

I was also considering a smaller setup for city living but it really requires roof access for the solar panels (perhaps 3x small 200w solar panels would be enough). A smaller chest freezer converted to a fridge along with cob lighting, etc but with 2 or 3 swap-able 1.5kwh batteries that can also power an ebike. My ebike will go about 40-50 miles at 15mph without pedaling on a 1.5kwh battery. Those batteries would probably only weigh about 15lbs each using the newer 3400ah 18650 cells. 

I did give this a lot of thought but I do not have any experience with actually using solar panels so I welcome criticism. I did research the cob lighting and they are wonderful, and by underpowering them they can be used with just a heatsink and no fan for very high efficiency. I have also been car free for 2.5 years now and I put at least 1000 miles a year on the e-bike, we were getting about 300-400 miles per $1 of electricity in the USA. You can build an inexpensive ebike too, most bikes can be converted with a mid drive motor in place of the cranks (so the motor uses the gears) or a rear wheel hub motor (if not riding up steep hills). I am using 3 power tools batteries connected to make a 56.8v 5ah battery that will go about 10 miles on a charge, I paid $70 for all 3 batteries and the charger. The mid drive motor cost me under $275 (I think they are $350-400 now), and then you just need a bike. Some people have made some nice ebikes using plus width tire $125 Mongoose bikes from Walmart by adding a motor and a battery.


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## Strontium (Sep 16, 2015)

Hi, I think you have the right ideas as there is not one solution for everyone need. If you want to go deeper into the subject of solar PV then there's free MOOG course from Delft Uni = naturally in English - https://www.edx.org/course/solar-energy-3) which is updated and possibly starts today. They also do other free courses on similar subjects and build stuff like this solar powered hydrofoil (



). Cooking with gas in some places uses a "bag" of organic waste which decomposes without air to produce methane which is then uses for cooking and the remains are compost, bio generators do this on a bigger scale and run generators from the methane, as this is plant waste it is a renewable resource in taking co2 from the air then releasing it again. I was running an a XUD engined diesel car and a 403cc diesel engined Yamaha motorbike on vegetable oil - permitted in the UK if under 2250 litres of oil consumed each year, the oil was not processed so counted as renewable and often can be classed a waste from cooking. Storage battery technology, capacity and prices are all changing with the goal of having sufficient capacity to charge during the day and run a house + car I use cob lights in an indoor bubble wrap "green house" to germinate plants with the heat and light, a few little fans for ventilation and a peltier to remove moisture all run on 12v battery by an Arduino nano with the idea of scaling it up and run from solar pv, starting plants 6 weeks before they would grow outside give bigger earlier crops with less diseases and allows a second crop of green manure. If you are going to try running everything on PV then Portugal is one of the places which has sun and space and a reasonably relaxed attitude to people doing their own thing but a difficulty with expediting official paperwork


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## John and Cecil (Dec 22, 2019)

Strontium said:


> Hi, I think you have the right ideas as there is not one solution for everyone need. If you want to go deeper into the subject of solar PV then there's free MOOG course from Delft Uni = naturally in English - https://www.edx.org/course/solar-energy-3) which is updated and possibly starts today. They also do other free courses on similar subjects and build stuff like this solar powered hydrofoil (TU Delft – Dreamteam Solar Boat Team - YouTube). Cooking with gas in some places uses a "bag" of organic waste which decomposes without air to produce methane which is then uses for cooking and the remains are compost, bio generators do this on a bigger scale and run generators from the methane, as this is plant waste it is a renewable resource in taking co2 from the air then releasing it again. I was running an a XUD engined diesel car and a 403cc diesel engined Yamaha motorbike on vegetable oil - permitted in the UK if under 2250 litres of oil consumed each year, the oil was not processed so counted as renewable and often can be classed a waste from cooking. Storage battery technology, capacity and prices are all changing with the goal of having sufficient capacity to charge during the day and run a house + car I use cob lights in an indoor bubble wrap "green house" to germinate plants with the heat and light, a few little fans for ventilation and a peltier to remove moisture all run on 12v battery by an Arduino nano with the idea of scaling it up and run from solar pv, starting plants 6 weeks before they would grow outside give bigger earlier crops with less diseases and allows a second crop of green manure. If you are going to try running everything on PV then Portugal is one of the places which has sun and space and a reasonably relaxed attitude to people doing their own thing but a difficulty with expediting official paperwork


You have some very interesting ideas. Thank you for the link to the solar course, I will be sure to study it once I have time.  With just Cecil and me we do not have a lot of organic waste and we don't use a lot of oil. Perhaps something can be devised to work with composting toilets, but will this generate enough usable gas to eliminate the need for cooking gas. I was leaning toward an efficient natural gas/propane system for cooking and an on-demand tankless water heater. For one or two people a tankless water heater can be quite efficient. Perhaps a solar water heater can be devised instead though.

Yes the cobs are great for growing plants too, that is how I found them as well. I like the greenhouse idea too. There is an interesting webpage I saw a couple years ago where a man built a greenhouse that was half underground. He then laid several hundred feet of pipe a few feet under the ground to form a big loop. He had fans on both ends of the pipe to circulate the air through the pipe and into and out of the greenhouse. In the winter it warmed and in the summer it cooled the greenhouse.

Something I have not considered too much is heating the home. I like the underground pipe idea for heating and cooling a home, but it would probably need a way to remove moisture from the air. Perhaps using the basement of the home as a winter grow room using cob lighting and recirculated underground air would help to heat the home a bit while also getting plants ready for the spring growing season. Besides heating the floor of the living portion of the home maybe some air can be brought up from the basement into the home and filtered some way to remove the moisture. I have also been looking into masonry heaters that will burn wood more efficiently for heat. Maybe there is a way to combine the two systems to remove the moisture from the basement air.

Ideally I would love to have a little farm of 1/2 -1 hectare, and it would be great if it was either on or near the water. I have also been researching small solar powered fishing boats. I like this guy's design, it is very simple and he uses no batteries. I think I would prefer to use an ebike battery with it though to increase range and power distribution during less sunlight, and also be able to tilt the canopy to increase power when the sun is not overhead.






It would also be nice to be able to use solar panels and batteries in a modular way so that each can be used for several different uses. I.e solar panels can be used on a fishing boat, or towed on a trailer to charge a vehicle, or connected to the main solar array to increase power to the home and charge the batteries. Batteries can be swapped and used for either powering the home, boat, vehicle, ebike, farming equipment, etc. Extra panels added to the system in the summer would allow for higher power usage during the day (like for air conditioning) or in the winter (an array of cobs for heating and starting plants to be moved outside in the spring). Modular batteries can help power the home during large periods of less sunlight like during a large storm system, etc.


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## Strontium (Sep 16, 2015)

Ahhhhh, I have been looking at little second-hand boats and electric outboards as there the river Zezere was dammed in several places years ago thus forming vast , very clean, lakes and two stroke engines are banned. Fishing licence available from a bank ATM and almost no restrictions if your boat is small. The odd speed boat are active but the area is so large and many "inlets" but the banks are steep so difficult to fish from the bank. I was looking for 55lb thrust outboard from 12v battery power and a PV panel on a large diameter pipe frame which could be put floating in the water when fishing. I've used similar commercial setups in remote areas to power radio repeaters. I think there's boaty fishing people on this forum who are near the river. For most PV systems it's the difficult balance between power produced/storage/power used with allowances for occasional worst case scenarios which makes it difficult to implement.. Portugal has invested in renewable s and partly due to the low population density in 80% of the country it does well on local power generation as in 

http://www.climateaction.org/news/portugal-runs-on-renewable-power-for-the-whole-of-march


https://www.google.com/maps/@39.578513,-8.2349694,12.5z


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## John and Cecil (Dec 22, 2019)

Strontium said:


> Ahhhhh, I have been looking at little second-hand boats and electric outboards as there the river Zezere was dammed in several places years ago thus forming vast , very clean, lakes and two stroke engines are banned. Fishing licence available from a bank ATM and almost no restrictions if your boat is small. The odd speed boat are active but the area is so large and many "inlets" but the banks are steep so difficult to fish from the bank. I was looking for 55lb thrust outboard from 12v battery power and a PV panel on a large diameter pipe frame which could be put floating in the water when fishing. I've used similar commercial setups in remote areas to power radio repeaters. I think there's boaty fishing people on this forum who are near the river. For most PV systems it's the difficult balance between power produced/storage/power used with allowances for occasional worst case scenarios which makes it difficult to implement.. Portugal has invested in renewable s and partly due to the low population density in 80% of the country it does well on local power generation as in
> 
> Portugal runs on renewable power for the whole of March - Climate Action
> 
> ...



Thank you for the link, I will look into that area too. I was recently looking online at a similar dammed area SW of that area (Alqueva/Mourao/Cheles). I also was looking at the northern border with Spain.

My boat preferences are probably a little different. I like to slow speed troll for fish, either with downriggers down deep or using a planer board to the side. Trolling speeds are usually between 2-3 mph so a small aluminum boat with a 30-50 lb trust electric motor is fine for me. I can always row the boat with oars too since it is light. A 36 lb thrust motor draws 350watts at full speed so a 1.5kwh battery can give 4hours of full power run time. A sunny or partly cloudy day with 2x 200w solar panels should give another 5 hours of full speed runtime. 

For someone who is anchored or drift fishing then I can see the advantages of a floating solar array. Perhaps it can be put on inflatable pontoons or an air mattress and you can run an electric inflator/deflator off the solar panels. Solar panels have come a long way and now they can be very light and they are able to be flexed. They have nice 200w panels that rv'ers use in the USA that are very thin and flexible, they only weigh about 3kg each and they are about 4' x 3'. An aluminum or pvc frame would probably not add too much weight to the solar array. 

I have recently been looking into another way to fish. It looks like a great way to fish in the ocean. You use a heavy duty high capacity deep sea rod and reel. You bait the hook and then connect the line to a drone and fly the baited hook out up to a mile offshore and then drop it, and then fly the drone back and recharge it while you wait for a fish.  I have watched videos of people fishing from a beach for tuna this way, some of them even use the drone camera to look for fish and then drop the bait on top of them.


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## Heizen (Nov 29, 2020)

These days, many homeowners prefer cheaper and environmentally safer alternatives for heating. One of the best ways is none other than solar heating. Not only is this method safer and better for the environment as compared to electric heating, but it is also more affordable because the energy is gotten from the same energy that comes from the sun.


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