Author Topic: Solar PV is now the most cost efective energy source.  (Read 37066 times)

0 Members and 1 Guest are viewing this topic.

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Solar PV is now the most cost efective energy source.
« on: January 09, 2017, 10:33:18 pm »
While hard to believe Solar is the most cost effective energy source at least for individual use not sure about large scale production.
I live in a cold but relatively sunny climate and after evaluating all energy sources for my offgrid house I decided that I will be using solar PV energy to heat my house.
Currently I use propane that is an order of magnitude more expensive about 25 cent/kWh vs just 2.4cent/kWh for PV panels.
Most people in the world use a mix of grid electricity and natural gas for house energy needs where natural gas is significantly less expensive than electricity (at least 4 to 5x) per unit of energy so house heating and hot water that is usually more than half of a typical house energy needs is delivered by natural gas.
Heating with solar PV panels can be extremely simple. Just connect a long wire with appropriate resistance to the PV panel output and you just made a completely solid state heater. You can drop that cable in water and you made a water heater. Problem with this simple approach is that is not very efficient best case 80% efficient in a clear sunny day with perfectly calculated resistive element and can be lower than 20% efficient in a completely overcast day.
That is why I came up with a simple but effective solution called Digital MPPT thermal controller (no expensive and unreliable DC-DC converters involved).

If you are curios on how Digital MPPT thermal controller works you can read my presentation about that here http://electrodacus.com/DMPPT450/dmppt-presentation-v01.pdf it is Open Source so there are no secrets all is explained and I think is educational even if you are not interested in the Digital MPPT thermal controller.




Yes the DMPPT450 will be on Kickstarter together with new version of SBMS but what I'm most interested in is your opinion about the Solar PV heating (cooling also possible using peltier elements but I need no cooling at my location in Canada and even where cooling is needed it represents a much smaller percentage of the total house energy use so is less important).   

 :palm: Below there is a long discussion regarding heat pumps and their COP (Coefficient of performance) when cascaded (two stage) please ignore all since I was wrong about the COP o such a system and if you want the correct answer you can see first post in page 3.
« Last Edit: January 19, 2017, 03:55:28 am by electrodacus »
 
The following users thanked this post: SeanB, TheAmmoniacal, dekra54, cmhansen, azerimaker

Offline TechnicalBen

  • Contributor
  • Posts: 37
  • Country: gb
Re: Solar PV is now the most cost efective energy source.
« Reply #1 on: January 09, 2017, 11:54:15 pm »
Are you considering lifespan costs?
I've only done back of the napkin stuff myself for "pie in the sky" imaginary projects. But I was getting the same cost as a small gas/petrol/diesel heater but a more elegant solution to burning stuff. Batteries were the biggest possible cost, so other forms of storage (heat sinks underground etc) could work out better. But I did read up that Solar uses more carbon in production than it saves in use... and can at times miss energy or economic returns too.

But it is entirely dependent on the sale and install price, along with the expected lifespan. And the stuff I've read relates to industrial/national production not small scale home use...
 

Offline djacobow

  • Super Contributor
  • ***
  • Posts: 1150
  • Country: us
  • takin' it apart since the 70's
Re: Solar PV is now the most cost efective energy source.
« Reply #2 on: January 10, 2017, 12:39:06 am »
At the utility scale, in places with good solar resource, PV can indeed be cheaper than prevailing sources (gas combined cycle, coal) on a /kWh basis. PV advocates call this "grid parity" -- and it is a real thing. PV is usually not cheaper than wind in windy places, but many places are not suitable for that.

However, you cannot run a power system from PV alone (the sun is intermittent, not dispatchable, and doesn't shine at night), so the /kWh basis is not quite the right way to think about.

Furthermore, there is an interesting phenomenon in places with lots of PV penetration, where the existence of the PV actually makes the output from the gas plant _appear_ more expensive on a /kWh basis. It happens when the owners of a gas- or coal-powered resource needs to recoup the cost of the plant over smaller and smaller kWh sales, because that utility is getting more energy from PV and wind. What's interesting in this case is that the gas or coal plant is still needed (because of flexibility) but much less energy is needed from it.


As for residential solar for heating, why not just heat your storage medium / working fluid directly? Why go through the electrical step? It will make substantially more efficient use of the sunlight. The technology for this has existed for a very long time.
 

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Solar PV is now the most cost efective energy source.
« Reply #3 on: January 10, 2017, 01:31:35 am »
Are you considering lifespan costs?
I've only done back of the napkin stuff myself for "pie in the sky" imaginary projects. But I was getting the same cost as a small gas/petrol/diesel heater but a more elegant solution to burning stuff. Batteries were the biggest possible cost, so other forms of storage (heat sinks underground etc) could work out better. But I did read up that Solar uses more carbon in production than it saves in use... and can at times miss energy or economic returns too.

But it is entirely dependent on the sale and install price, along with the expected lifespan. And the stuff I've read relates to industrial/national production not small scale home use...

I use cost amortization for comparison as you probably seen in the pdf document.
As a simple example PV panels cost amortization is 2.4 cent/kWh  (USD) (based on 80 cent/Watt acquisition cost, 25 year amortization period and amount of solar at my location).
petrol for example is now here about 70cent/liter and one liter contains about 9.5kWh of energy/liter so cost is 7.4 cent/KWh significantly higher than PV cost amortization.
This is not all a Gasoline (petrol) burner will not be 100% efficient and be more complex less reliable compared to a simple resistive heat element needed for PV heating and that will make a heater based on petrol significantly more expensive when all that is considered burner, pipes, heat exchanger maybe pumps....
Natural gas is for sure the cheapest form of fossil fuel and that is why I used that in my comparison showing that even that can not compete with direct PV heating and thermal mass storage.

Is extremely wrong to say solar PV panels require more energy to produce than they generate over their life. If that will be true the cost of PV panels will be much higher than it is since you need to pay for that energy when you buy the panel.
The amount of energy used to produce a PV panel can be produced by the panels in just 2 to 4 months. So yes you can build a profitable PV panel factory powered with PV solar energy.

At the utility scale, in places with good solar resource, PV can indeed be cheaper than prevailing sources (gas combined cycle, coal) on a /kWh basis. PV advocates call this "grid parity" -- and it is a real thing. PV is usually not cheaper than wind in windy places, but many places are not suitable for that.

However, you cannot run a power system from PV alone (the sun is intermittent, not dispatchable, and doesn't shine at night), so the /kWh basis is not quite the right way to think about.

Furthermore, there is an interesting phenomenon in places with lots of PV penetration, where the existence of the PV actually makes the output from the gas plant _appear_ more expensive on a /kWh basis. It happens when the owners of a gas- or coal-powered resource needs to recoup the cost of the plant over smaller and smaller kWh sales, because that utility is getting more energy from PV and wind. What's interesting in this case is that the gas or coal plant is still needed (because of flexibility) but much less energy is needed from it.


As for residential solar for heating, why not just heat your storage medium / working fluid directly? Why go through the electrical step? It will make substantially more efficient use of the sunlight. The technology for this has existed for a very long time.


Wind in the end is still solar energy but for small scale even in windy locations like mine are not cost effective when compared to solar PV and they are more intermittent requiring a larger storage capacity.

If you check the document the thing that makes the DMPPT450 cost effective and possible is the combination of cheap PV panels with cheap thermal mass energy storage below 0.5cent/kWh to store energy in thermal mass.
The large thermal mass and large size PV array to provide the house with heating also helps reduce the Lithium battery storage to at least half thus helping also reduce the cost of electrical energy needed for appliances in the house.
I will need no backup energy source for my house and the DMPPT450 + SBMS + PV panels + large thermal storage + small LiFePO4 battery can make a house completely energy independent or a Net Zero energy house at a cost lower than traditional grid electricity + natural gas. For a new house difference is even higher because of the connection cost to those utilities.

The thermal solar was also used in my comparison and that is less cost effective than PV solar heating and less reliable. See page 5 for comparison table.
 
« Last Edit: January 17, 2017, 01:43:05 am by electrodacus »
 

Offline TechnicalBen

  • Contributor
  • Posts: 37
  • Country: gb
Re: Solar PV is now the most cost efective energy source.
« Reply #4 on: January 10, 2017, 08:44:08 am »
Yep, sorry, it was the carbon costs that may never balance out, not the electric production (with exception of really small badly made useless stuff :P ).
 

Offline Codebird

  • Regular Contributor
  • *
  • Posts: 161
  • Country: gb
Re: Solar PV is now the most cost efective energy source.
« Reply #5 on: January 10, 2017, 11:53:24 am »
Quote
As for residential solar for heating, why not just heat your storage medium / working fluid directly? Why go through the electrical step? It will make substantially more efficient use of the sunlight. The technology for this has existed for a very long time.

I can see one advantage: It's easily added to an existing array. If you already have a sizable PV, it's going to be over-capacity in summer. Once the batteries are full, the panels just sit there being a waste of capital investment. Diverting it into an immersion heater would cost very little (far less than fitting additional solar water heaters and associated plumbing and pump), and would at least take a bit off the gas bill.
 

Offline tggzzz

  • Super Contributor
  • ***
  • Posts: 19091
  • Country: gb
  • Numbers, not adjectives
    • Having fun doing more, with less
Re: Solar PV is now the most cost efective energy source.
« Reply #6 on: January 10, 2017, 01:55:03 pm »
Don't forget to include the cost of keeping the backup system operational for when the solar/wind/tidal power is unavailable.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline Kleinstein

  • Super Contributor
  • ***
  • Posts: 13947
  • Country: de
Re: Solar PV is now the most cost efective energy source.
« Reply #7 on: January 10, 2017, 02:19:40 pm »
It depends on the location on how effective PV is. The return can be about 3 times has high in a really sunny place like souther Spain / the desert SW of the US or inland Australia compared to to a place like England or northern Germany. It also depends o how volatile the sun is - not much fun with PV in the winter in Island (hardly any sun that time of year).

When using PV for an off grid application you will likely have a lot of unused energy in the summer, when you don't need heating and at a cold place still not much cooling either. So for such an application the used PV energy could be something like 1/2 or even less of the theoretical production. It gets even worse if you need extra capacity for bad wether phases if you don't have a lot of storage or a backup system.
The really low price of something like 3-5 cents is for 100% utilization. For a fair comparison one has to include storage and / or limited energy use/demand. So you very could well end up with much higher costs for the storage than for the PV modules.
 
The following users thanked this post: Someone

Offline Seekonk

  • Super Contributor
  • ***
  • Posts: 1938
  • Country: us
Re: Solar PV is now the most cost efective energy source.
« Reply #8 on: January 10, 2017, 03:13:27 pm »
Many years ago I started looking for a community where I could discuss RE ideas.  I've been pushing PV heating for years.  The RE community seems totally oblivious to the energy they waste.  After all it is free. I've heard comments of energy usage actually increasing. While this isn't the norm in the rest of the world, we have water heating tanks.  A small array of 300-600W is sufficient to provide some recovery and all the normal heat loss.  This small cost effective application is the only one that can guarantee 100% of solar energy from the panel is used.  Grid tie seems ideal, but the utilities don't want  you dumping into the grid and that energy is worthless in payback, it will only get worse.
 

Offline CJay

  • Super Contributor
  • ***
  • Posts: 4137
  • Country: gb
Re: Solar PV is now the most cost efective energy source.
« Reply #9 on: January 10, 2017, 03:54:00 pm »
I might be missing something crucial here but:

If it's purely for heating would it not be better to harvest the sunlight using evacuated water heating tubes that can have up to 90% efficient conversion rather than converting it to electricity at some order of magnitude lower efficiency and using that to heat your property?

Sure, you've still got a need for electricity to run pumps, valves etc. but far less of it.

 

Offline Seekonk

  • Super Contributor
  • ***
  • Posts: 1938
  • Country: us
Re: Solar PV is now the most cost efective energy source.
« Reply #10 on: January 10, 2017, 04:13:35 pm »
That is what they teach you in school, but lacks a sense of reality.  These systems freeze, leak, break down and are complicated to install.  Running a wire is easy. A recent home repair program quoted these systems at $10,000 to 15,000 to just heat daily water.  Every case is different.  I have a summer home and all hot water is PV, my other home is heat pump hot water.
 
The following users thanked this post: mmagin

Offline Kleinstein

  • Super Contributor
  • ***
  • Posts: 13947
  • Country: de
Re: Solar PV is now the most cost efective energy source.
« Reply #11 on: January 10, 2017, 04:33:44 pm »
Though simpler technology the solar thermal systems are more complicated to install (tubes instead of wires) and need more maintenance. Efficiency is somewhat higher, but not reaching 90%, more like 50% - as they have difficulties at low intensity and already something like 10% are lost due to reflection. Still you would need something like 2 to 5 times the area with PV.

Well done, they do work well and $10000 would already be a relatively large system. Also the PV system would also need all the water tank and related parts - which is likely included in the $10000 sum. A poor made solar-thermal system can be a maintenance nightmare - I friend just shut down his system, because he needed a new pump and liquid essentially every second year or so. So it did not work, despite of a very sunny place.
 

Offline CJay

  • Super Contributor
  • ***
  • Posts: 4137
  • Country: gb
Re: Solar PV is now the most cost efective energy source.
« Reply #12 on: January 10, 2017, 04:41:34 pm »
Ah so the complexity trade offs and increased maintenance requirements make them more expensive an investment so even though the headline efficiency is much higher than PV, PV wins through reliability if the water system is badly implemented plus you have a simpler option for local energy storage.

Been a long time since I was at school so it's always a learning experience here.

 
 

Offline tggzzz

  • Super Contributor
  • ***
  • Posts: 19091
  • Country: gb
  • Numbers, not adjectives
    • Having fun doing more, with less
Re: Solar PV is now the most cost efective energy source.
« Reply #13 on: January 10, 2017, 05:38:05 pm »
That is what they teach you in school, but lacks a sense of reality.  These systems freeze, leak, break down and are complicated to install.  Running a wire is easy. A recent home repair program quoted these systems at $10,000 to 15,000 to just heat daily water.  Every case is different.  I have a summer home and all hot water is PV, my other home is heat pump hot water.

Well, of course without imagination you can design expensive systems. OTOH you can often get 80% of the benefit with a small fraction of the cost.

Such "80%" installations: http://www.365ecology.com/shop/solar-water-heater/megasun-200-lt-greece/ feeding one or two taps are commonplace around the mediterranean.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline mtdoc

  • Super Contributor
  • ***
  • Posts: 3575
  • Country: us
Re: Solar PV is now the most cost efective energy source.
« Reply #14 on: January 10, 2017, 06:07:10 pm »
That is what they teach you in school, but lacks a sense of reality.  These systems freeze, leak, break down and are complicated to install.  Running a wire is easy. A recent home repair program quoted these systems at $10,000 to 15,000 to just heat daily water.  Every case is different.  I have a summer home and all hot water is PV, my other home is heat pump hot water.

Well, of course without imagination you can design expensive systems. OTOH you can often get 80% of the benefit with a small fraction of the cost.

Such "80%" installations: http://www.365ecology.com/shop/solar-water-heater/megasun-200-lt-greece/ feeding one or two taps are commonplace around the mediterranean.

Whether you can do a simple, low cost direct solar hot water system is site dependent.  A climate where temperatures never drop below freezing presents many options for very simple systems but even these are subject to corrosion issues.  A simple drainback system will work for a location with the occasional freeze but adds a level of complexity. In areas with more regular and deeper freezing the systems get much more complicated.  The points of failure and the need for maintenance quickly goes up.

As others have stated, the reason PV heated water makes sense now is because of the drop in PV panel prices.  PV panels are virtually maintenance free with a lifespan of 25+ years. If one already has a PV electric system and has the real estate (roof or ground mount) to add more panels it is a no brainer to do that and heat water with PV rather than install a separate direct solar water heating system.   

Those with battery based PV systems (off grid or grid tie with backup) can configure their system to divert any excess power (once batteries are topped off) to water heating.  Some of the bettter charge controllers (eg the Midnite Classic) have programmable auxillary outputs that can be easily set up to drive a SSR based on battery SOC to accomplish this.
« Last Edit: January 10, 2017, 06:08:56 pm by mtdoc »
 

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Solar PV is now the most cost efective energy source.
« Reply #15 on: January 10, 2017, 06:43:17 pm »
Just launched the Kickstarter a few minutes ago.
Yep, sorry, it was the carbon costs that may never balance out, not the electric production (with exception of really small badly made useless stuff :P ).

Carbon cost is dependent on the energy source you are using. You can use solar PV to manufacture solar panels.
If you are going to use energy then building solar panels is the best way if carbon cost is important to you.

Don't forget to include the cost of keeping the backup system operational for when the solar/wind/tidal power is unavailable.

I do not need any backup because of the large and inexpensive thermal mass storage.

It depends on the location on how effective PV is. The return can be about 3 times has high in a really sunny place like souther Spain / the desert SW of the US or inland Australia compared to to a place like England or northern Germany. It also depends o how volatile the sun is - not much fun with PV in the winter in Island (hardly any sun that time of year).

When using PV for an off grid application you will likely have a lot of unused energy in the summer, when you don't need heating and at a cold place still not much cooling either. So for such an application the used PV energy could be something like 1/2 or even less of the theoretical production. It gets even worse if you need extra capacity for bad wether phases if you don't have a lot of storage or a backup system.
The really low price of something like 3-5 cents is for 100% utilization. For a fair comparison one has to include storage and / or limited energy use/demand. So you very could well end up with much higher costs for the storage than for the PV modules.

Yes location is important. I live in a very cold location Saskatchewan, Canada but also decently (more than decently) sunny in winter. The advantage of solar is that even in the worst overcast day you still get some energy (you can see a daily energy graph for a full year on my location to get a better idea).
Yes is true about unused energy in offgrid application but including that cost is still better than grid when heating and electricity is combined. And yes in cold places like mine I need no house cooling (if house is properly done there are plenty of houses here with air conditioning) but also winter is longer with 5 to 6 months of heating season.
PV panel amortization cost is 2.4 cent/kWh so even if you use just half of the energy in average over a year that will double the cost of used energy to 4.8cent/kWh still quite decent.
The thermal storage amortization cost is extremely low at just 0.5 cent/kWh so you can have as much capacity as you need depending on your location and amount of sun.
When heating and electricity is combined you oversize first the thermal storage that is the least expensive then PV array and keep the LiFePO4 battery as small as you can get away with since that has a real world cost amortization of 25 cent/kWh and there is nothing better than LiFePO4 for storage.

I might be missing something crucial here but:

If it's purely for heating would it not be better to harvest the sunlight using evacuated water heating tubes that can have up to 90% efficient conversion rather than converting it to electricity at some order of magnitude lower efficiency and using that to heat your property?

Sure, you've still got a need for electricity to run pumps, valves etc. but far less of it.



It is not and in the document I make the case for that comparing PV with thermal solar (evacuated tubes) and Natural gas. Better efficiency does not equate with better cost amortization.

That is what they teach you in school, but lacks a sense of reality.  These systems freeze, leak, break down and are complicated to install.  Running a wire is easy. A recent home repair program quoted these systems at $10,000 to 15,000 to just heat daily water.  Every case is different.  I have a summer home and all hot water is PV, my other home is heat pump hot water.

Yes thermal solar has problems if not properly installed or bad quality parts are used but even if you not include the maintenance and repair cost is still more expensive than PV solar at this point.

I see most of you did not read or look at the pdf that answers all or almost all question posted here but I get that since if you are not that interested in this you do not want to read a 15 page document (mostly graphs not that much text).

The claim is that this is the most cost effective house energy solution at my location and probably many other locations.


   

Offline tggzzz

  • Super Contributor
  • ***
  • Posts: 19091
  • Country: gb
  • Numbers, not adjectives
    • Having fun doing more, with less
Re: Solar PV is now the most cost efective energy source.
« Reply #16 on: January 10, 2017, 06:53:35 pm »
That is what they teach you in school, but lacks a sense of reality.  These systems freeze, leak, break down and are complicated to install.  Running a wire is easy. A recent home repair program quoted these systems at $10,000 to 15,000 to just heat daily water.  Every case is different.  I have a summer home and all hot water is PV, my other home is heat pump hot water.

Well, of course without imagination you can design expensive systems. OTOH you can often get 80% of the benefit with a small fraction of the cost.

Such "80%" installations: http://www.365ecology.com/shop/solar-water-heater/megasun-200-lt-greece/ feeding one or two taps are commonplace around the mediterranean.

Whether you can do a simple, low cost direct solar hot water system is site dependent.  A climate where temperatures never drop below freezing presents many options for very simple systems but even these are subject to corrosion issues. 

Greek beaches this week :)
http://www.bbc.co.uk/news/world-europe-38550369

And site-specific factors are why unqualified statements shouldn't be made!
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Solar PV is now the most cost efective energy source.
« Reply #17 on: January 10, 2017, 07:18:53 pm »
Greek beaches this week :)
http://www.bbc.co.uk/news/world-europe-38550369

And site-specific factors are why unqualified statements shouldn't be made!

:) That will happen but Greece is and will remain a great place for solar energy.
I remember when I visited Greece many houses had hot water heaters on the roof.

Offline Seekonk

  • Super Contributor
  • ***
  • Posts: 1938
  • Country: us
Re: Solar PV is now the most cost efective energy source.
« Reply #18 on: January 10, 2017, 07:28:39 pm »
Least anyone forget it, PV is high quality energy.  You can do something with it in the summer and winter.  What does an evacuated tube get you in the summer?
 

Offline coppice

  • Super Contributor
  • ***
  • Posts: 8538
  • Country: gb
Re: Solar PV is now the most cost efective energy source.
« Reply #19 on: January 10, 2017, 07:56:18 pm »
Least anyone forget it, PV is high quality energy.  You can do something with it in the summer and winter.  What does an evacuated tube get you in the summer?
Baths and showers. Most of the places I know with a high concentration of evacuated tube solar heaters have little need for space heating. They use it exclusively for hot water, which they tend to need more of in hot weather - people sweat more and shower more in hot weather - although the temperature rise they need to achieve at that time is smaller than in cold weather.
 

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Solar PV is now the most cost efective energy source.
« Reply #20 on: January 10, 2017, 08:05:50 pm »
Least anyone forget it, PV is high quality energy.  You can do something with it in the summer and winter.  What does an evacuated tube get you in the summer?

I think I mentioned this in the pdf.  For my case the extra energy can keep the LiFePO4 battery smaller since the DMPPT can fully charge the battery in an overcast day by redirecting up to the entire heating array to battery charging when needed.
While it is high quality energy is still hard to find a use for so much excess energy in summer.
One thing that I will be using it is to distill water (we drink distilled water about 4 liter/day and at the moment we buy that for $2/day). While just 10% of the energy from all that excess will be needed to distil 4liters/day of water the savings of $2/day over 25 years will add up to $2 x 365 x 25 = $18250 and this saving alone can pay for the entire installation (more actually).
This is a particular case that we can ave by making our own distilled water for drinking but still is just 10% of the excess.
I realy have no other ideas on where I can use the excess in summer that is around 1MWh/month. Even not using the excess at all this is still more cost effective than any other source as seen in the comparison table where excess energy was considered lost/unused.

Sometimes people try so much to use this excess than they end up spending more than if just not using the excess. 

 

Offline cmhansen

  • Contributor
  • Posts: 26
  • Country: us
Re: Solar PV is now the most cost efective energy source.
« Reply #21 on: January 12, 2017, 01:05:15 pm »
PV for heating is ideal ok.  Evacuated tubes fall linearly on efficiency if you look at the data (and heat flux formula):
http://www.heliodyne.com/wp-content/uploads/2016/03/Evacuated-Tube-Comp.pdf

More simply CSP at even 200C is still considered 'waste heat' as basically stated earlier and for good reason.  If you want to heat a pool by a degree or two CSP 'waste heat' is probably more efficient, but not if you want a tank of 60C water.  You can of course get relatively 'high-grade' heat through molten salt (and a steam turbine for electricity), but do you want that over PV for home at a higher cost?  No, and if one is simply using heated water as a working fluid, it really is classified as waste heat that isn't even useful for hot water (only as a limited pre-heater).
https://en.wikipedia.org/wiki/Waste_heat#Disposal

I've written a detailed idea before as well about using an extra heatpump to buffer heating or cooling in a tank of water vs batteries - much more direct than geothermal.  This would work as good for non-solar.  It is geothermal except air-source and buffered daily not seasonally.  Peltier is not (yet) good for cooling at <10% efficiency.  In addition for heating, if you had super-icephobicity coating on a heatpump you could use it in colder periods.  Ideally batteries are the best and most direct buffer, we'll replace heatpumps for heating before we do for cooling.

And in fact look at current cost of batteries at nearly $100 / kWh (almost there but it will surely get there soon), at standard 2k cycles this is only $.05 / kWh of battery use.  Panels are looking more like $.01 / kWh now... if you use batteries 2/3 the time you easily see (.01 x3 + .05 x2)/3 = $.04333 average per kWh, grid cost alone exceeds this and 'free fusion' would end up costing more!

And a tricky counter-intuitive bit about amortized cost of the panel not factoring in land cost - tracking actually increases this (for high-insolation areas doubly so!)  The reason is simple that the higher proportion spent at higher temps, the lower the lifespan (degradation per degree rise).  Meaning colder climates with fixed angle have the least normalized temp degradation per kWh produced, and therefor least cost, and since tracking takes more land than fixed per kWh (I think) this is even more in favor of fixed.  (Also consider seasonal tracking is (substantially?) more productive than daily tracking, if highest power per area is needed).

Yes many are told solar takes more energy than it can produce.... though one study I read had solar at 7x, wind something like 21 and nuclear the highest by an order or more).  Plus this will only go way down if we get away from thick silicon wafers.  Here is a fairly current and concrete (not forcasted) estimate of EPBT that shows solar in an even better 'light':
http://www.apricum-group.com/electricity-payback-time-pv-system-facts/
That is 12.5x - 25x total energy payback (including inverters and BOS) over 25 years!  I'm not sure if variable wafer cutting loss is accounted for in that figure, it might assume 'kerfless':
https://www.greentechmedia.com/articles/read/1366-Technologies-to-Build-250MW-Direct-Silicon-Wafer-Factory-in-Upstate
Regardless no dead birds, burning windmills, bad bearings or massive transmissions to overhaul.
« Last Edit: January 24, 2017, 02:34:54 am by cmhansen »
 

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Solar PV is now the most cost efective energy source.
« Reply #22 on: January 12, 2017, 10:37:13 pm »
Thanks for the detailed comment cmhansen

I've written a detailed idea before as well about using an extra heatpump to buffer heating or cooling in a tank of water vs batteries - much more direct than geothermal.  This would work as good for non-solar.  It is geothermal except air-source and buffered daily not seasonally.  Peltier is not (yet) good for cooling at <10% efficiency.  In addition for heating, if you had super-icephobicity coating on a heatpump you could use it in colder periods.  Ideally batteries are the best and most direct buffer, we'll replace heatpumps for heating before we do for cooling.

I considered heat pump before but the PV energy is so cheap that trying to use a heat pump will not make economic sense. It will when compared to battery but not with my method where battery is not used for heating so cost is extremely low.
Peltier is extremely efficient if used properly as a heat pump and I will do probably a youtube video about that soon. Most care about profit so they use the peltier element at full or almost full rated power but if used at just a fraction of the full power the peltier can be extremely efficient so COP of 3 can be obtained with careful design.
Here is the spec http://www.thermonamic.com/TEC1-12706-English.PDF of a very common peltier element that cost maybe 2 or $3 in China. Check last page and you can see when used at 3V will take about 1A so 3W of power and be able to pump about 12W when 10C delta is used. For high delta using two or 3 stages may be needed the COP will still remain the same.
When the peltier element is used close to full power say 12V and higher temp delta then module is an order of magnitude less efficient with COP well below 1
Of course the cost complexity of the cooling with peltier needs to be weighted against very low cost of PV energy and some compromise between cost/complexity and efficiency can be selected.

And in fact look at current cost of batteries at nearly $100 / kWh (almost there but it will surely get there soon), at standard 2k cycles this is only $.05 / kWh of battery use.  Panels are looking more like $.01 / kWh now... if you use batteries 2/3 the time you easily see (.01 x3 + .05 x2)/3 = $.04333 average per kWh, grid cost alone exceeds this and 'free fusion' would end up costing more!

The cost of battery per storage capacity is not a good indication of anything. Also those $100/kWh (I'm sure are more like $200/kWh today) and only have 500 cycles at 100% DOD so please provide a spec and real price if you have something in mind that can be had today.
LiFePO4 are by far the most cost effective for electrical energy storage and the higher energy density cells while make sense in consumer EV for a few reasons are far from cost competitive in therms of energy storage.
Best real life cost amortization for LiFePO4 currently available is around 25 cent/kWh. The theoretical based on simple calculation as the one you did before is much lower but that is not including the battery aging that affects all batteries much more even than cycle life.
My cost amortization for PV panels of 2.4cent/kWh (USD) is based on (80 cent/Watt acquisition cost, 25 years amortization period and amount of solar at my location ).
While is true that you may be able to get better than 80cent/Watt as PV panel acquisition cost (just seen 67cent/Watt in a US online store) and some panel manufacturer warrant power output up to 30 or 35 years and maybe some areas get slightly more solar than my location the 2.4 cent/kWh is still low enough to make my point that solar PV is the lowest cost of energy currently available for powering an individual house.
With the DMPPT450 and SBMS combination the LiFePO4 can get a better cost amortization than 25cent/kWh (when only SBMS is used) close to half maybe as good as 12cent/kWh becose aging will play a lower role since battery will be smaller and more heavily used so it will last less in time but store more energy in that period (will be cycled more).

And a tricky counter-intuitive bit about amortized cost of the panel not factoring in land cost - tracking actually increases this (for high-insolation areas doubly so!)  The reason is simple that the higher proportion spent at higher temps, the lower the lifespan (exponential degradation per degree rise).  Meaning colder climates with fixed angle have the least normalized temp degradation per kWh produced, and therefor least cost, and since tracking takes more land than fixed per kWh (I think) this is even more in favor of fixed.  (Also consider seasonal tracking is (substantially?) more productive than daily tracking, if highest power per area is needed).

Mechanical solar tracking is for sure a long dead technology and best argument for that is to look at all large scale solar PV installations where 95% of them are fixed PV panels with no tracking at all.

Yes many are told solar takes more energy than it can produce.... though one study I read had solar at 7x, wind something like 21 and nuclear the highest by an order or more).  Plus this will only go way down if we get away from thick silicon wafers.  Here is a fairly current and concrete (not forcasted) estimate of EPBT that shows solar in an even better 'light':
http://www.apricum-group.com/electricity-payback-time-pv-system-facts/
That is 12.5x - 25x total energy payback (including inverters and BOS) over 25 years!  I'm not sure if variable wafer cutting loss is accounted for in that figure, it might assume 'kerfless':
https://www.greentechmedia.com/articles/read/1366-Technologies-to-Build-250MW-Direct-Silicon-Wafer-Factory-in-Upstate
Regardless no dead birds, burning windmills, bad bearings or massive transmissions to overhaul.

That is a false information solar PV can not take more energy to manufacture than it produces over is life.
Think about this way any solar PV manufacturer wants to have a profit and will buy energy in order to produce the panels.
Then you pay the cost of production (energy + materials + equipment + labor) + manufacturer profit + reseller profit + taxes.
A simple 250W PV panel can be had easy for $200
This panel will produce 380kWh/year at my location (an average location for solar nothing special).
So say just 25 years (panels can last and produce energy a lot longer) x 380kWh/year  = 9.5MWh of energy produced by that panel over is 25 years life.

$200/9500kWh = $0.021/kWh so I also calculated the cost amortization. For solar data go to PVWatt select Regina Saskatchewan, Canada as my location use panel tilt at 50 degree and 1kW PV array since it will not accept smaller then get than energy for a year and divide by 4 for a 250W panel and you will get that 380kWh number.

Now I'm extremely sure that PV panel total energy used will not be anywhere near 9.5MWh for a producing ans shipping a single panel and is probably more like the energy can be recovered in just the fist few months by the panel.
Do not forget that the cost of the PV panel includes so much more than just the energy used to manufacture and transport the panel. 

Online splin

  • Frequent Contributor
  • **
  • Posts: 999
  • Country: gb
Re: Solar PV is now the most cost efective energy source.
« Reply #23 on: January 13, 2017, 04:01:02 am »

Check last page and you can see when used at 3V will take about 1A so 3W of power and be able to pump about 12W when 10C delta is used. For high delta using two or 3 stages may be needed the COP will still remain the same.

No. For the second stage you need to provide another 3W of power to move the same 12W through another 10C delta. Plus an additional 3/12 * 3W to move the power added in the first stage, so the overall COP is now less than half that of the first stage. You end up with much the same COP as if you used a single stage. For large deltas, > 40C or so, you are forced to use multiple stages but the COP is terrible.
 

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Solar PV is now the most cost efective energy source.
« Reply #24 on: January 13, 2017, 06:18:23 am »
Check last page and you can see when used at 3V will take about 1A so 3W of power and be able to pump about 12W when 10C delta is used. For high delta using two or 3 stages may be needed the COP will still remain the same.

No. For the second stage you need to provide another 3W of power to move the same 12W through another 10C delta. Plus an additional 3/12 * 3W to move the power added in the first stage, so the overall COP is now less than half that of the first stage. You end up with much the same COP as if you used a single stage. For large deltas, > 40C or so, you are forced to use multiple stages but the COP is terrible.

You do not move the same 12W you move additional 12W.
Second stage will of course need to be a bit more powerful since it will need to move the 12W + 3W from the hot side of the first stage.
You forget that you get a 10C delta with single stage and 20C delta with two stage so is obviously more energy pumped.


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf