Let's burn more sunshine 4

[fast4door]

Climate change deniers, go away.

So let's say global warming is caused by pulling tightly-packed carbon out of the ground in solid/liquid form, then combining it with oxygen and creating more CO2 than there was previously. Let's also say we want to simply freeze the amount of CO2 in the atmosphere and dispense with this "sequestration" baloney. In that scenario, we would need a carbon-neutral course of energy. That leaves nuclear or solar or bio-fuels. I want to talk about bio-fuels.

Here's what I can't figure out. Nature has been capturing sunlight and turning it into carbohydrates and lipids for like a trillion years. There's tons of energy out there. We're really good at disassembling those hydrocarbon chains inside of cylinders, turbines, etc. We should be able get good old nature to make our fuel for us. Is there any hope to the people that want to make biodiesel from algae? Are the yields unrealistically low?

 

[TomDOT]

The main problems with algae are:

1) Scaling. It's proven at lab scale, someone was going to do a pilot scale. Nobody has it at industrial scale

2) Contamination/infestation. To be effective, you have to grow a high-oil species. If you get a single cell of a more competitive low-oil species, it can totally outgrow/swamp out your desired species.

Are these problems which can be overcome? Sure. Just not today or tomorrow. Big learning curve to climb.

And yes, there is a crapton of solar insolation available. I wish that people would do more "smart" microsolar. For example: Instead of building a carport/RV/patio roof and putting solar panels on that roof, use the solar panels AS the roofing/shading material. Double usage, reduced cost, multiple benefits.

Specific example: Wal-Mart has roughly 100,000 acres of parking lots in the USA, all of which are adjacent to a heavy-duty connection to the grid (for the store) meaning that infrastructure and transmission investment would be minimal. Wal-Mart could provide shaded parking as a benefit to customers (saving on AC demand in their cars) and at the same time produce a crapton of electricity.

Back of the envelope: Figure a conservative 5 kWh per square meter solar insolation, giving roughly 20 MWh per acre. Multiply by acreage to get 2 TWh solar insolation. Figure 10% areal conversion efficiency for both spacing losses and panel efficiency. So, 200 GWh available from Wal-Mart parking lots every day.

2011, the USA used 3,856 TWh of electricity, giving a daily average of 10.56 TWh. So, we could get about 2% of the US electric demand supplied from solar panels in Wal-Mart parking lots alone. As a bonus, it's mostly peak demand electricity - both daily peak, and annual peak. (I actually ran this calculation from a second set of base assumptions ending up with 2.4%, chose the more conservative result above)

Now consider how many more parking lots there are than just Wal-Mart.

 

[fast4door]

Just to be clear, a crapton is 1,000 petatons.

 

[cvg]

1) Walmart doesn't need covered parking. The stores are already packed out
2) Only the projects installed in the sunbelt region will be profitable
3) structural supports, DC to AC converters, transformers, cable and J-boxes and switched connection to the grid are still required. This is the bulk of the expensive infrastructure. In fact, the carport type structure would make it much more expensive than a typical solar farm with pier foundations.
4) walmart parking lots really aren't that large compared to commercial scale solar farms
5) Even with the taxpayer subsidies, the ROI is only marginally attractive

 

[TomDOT]

Mind if we use watt-hours? It actually can be made to work out.

5x10^14 square meters of earth's surface, 6kWh/square meter/day (average global solar energy. I used 5 above for the USA)

3.0x10^18 watt-hours/day. Divide by 10^15 for Peta.

3000 Petawatt-hours/day.

Let's allow 2/3 of the surface area as too difficult for current engineering (deep ocean)

1000 Petawatt-hours/day.

Done. One crapton of solar insolation per day.

 

[TomDOT]

cvg:

1) Opinion only.
2) It was an example of the energy available, not practical site selection.
3) Apparently you are unaware of the billions of dollars Texas is spending for new and upgraded transmission lines to handle a measly 10 GW (nameplate) of wind power. Also, don't be silly. The home carport and Wal-mart parking lot were two separate examples. You would optimize the structure in the parking lot, some additional cost to make sure it is high enough for cars to pass under cleanly.
4) Yep, it was an example of the energy available, using a scale familiar to virtually everyone here. It is also an example of multiple beneficial uses of the same property.
5) Ditto.

 

[KENAT]

TomDOT, is your 10% allowing for the fact that much of the parking lot is actually road way so maybe half the total parking lot area could realistically be used for solar panel car ports. I assume so but wanted to check.

As for Algae, there are a lot of problems with how to get the necessary light to all the algae - you end up needing a large effective surface area. Plus the algae like to stick to surfaces so simply using thin transparent pipes or chambers with lots of internal mirrors... get's tricky.

Plus there may be temperature limitations on the algae, and just the amount of water required might get to be an issue.

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[fast4door]

Does anybody know of a technique where solar is converted directly to chemical energy, just like plants? The problem with solar is the ROI sucks because the efficiency isn't good and the silicon is expensive. Can't we just convince some plant species to spit out sugar or something and then burn that? Like a maple tree, only less good on pancakes and more good in cylinders.

I saw something on This Old House a couple seasons ago that used a solar panel to generate current that was used to denature water, which was then stored in gas tanks to be recombined in a fuel cell. It solves the peak issue, but the problem again is the capex is huge due to the silicon and the platinum catalyst.

 

[TomDOT]

KENAT - as cvg mentioned, the "car port" design is sub-optimal for a real parking lot installation. "Car port" was more for a home car port/RV shade.

Panels for the parking lot can readily extend over the driving areas. Shade would be somewhat compromised by optimizing for electricity production, but shade is just a side benefit anyway.

 

[TomDOT]

fast4door - the silicon problem has largely been solved by the thin film PV guys. They use ~1% of the silicon you would find in a traditional PV panel. Efficiency was a problem at first, but they're over 14% now and still climbing.

 

[fast4door]

Okay, so 14%. That still seems low. But only because I'm thinking of a diesel engine which gets something like 30%. But maybe I'm off-base? The fact that we can see leaves on trees (and the fact they appear green) is evidence they're not capturing 100% of the light hitting them. Does anybody have an idea what the efficiency of a leaf is?

 

[moltenmetal]

TomDOT: The idea of dual- purpose roofing/solar collectors isn't new but isn't an economic reality yet either.

I assume you're joking, but naive calcs like the ones you just did are the reason that David MacKay wrote his "Alterative Energy Without the Hot Air" book. Have a look at his estimates for solar and compare against yours. His estimates are limit-state estimates, assuming money is no object. He looks at both solar thermal and solar photovoltaic, along with various biofuel options.

FYI, a Sharp 235 W polycrystalline panel measures 0.99m x 1.64 m or about 1.62 m2

http://files.sharpusa.com/Downloads/Solar/Products/sol_dow_ND235QCJ.pdf

A Toronto, Ontario solar installation can be expected to generate about 1175 kWh/yr per kW of panel nameplate capacity if installed at the optimal angle.

http://www.greentoronto.me/evaluating-solar-power-potential-in-ontario/

People in Ontario are willing to cough up the necessary capital to install such systems in return for the $0.60-$0.80/kWh feed-in tarrif that the government will pay them for power from a solar installation, but at $0.10/kWh, none would be built by anyone who cares about their money and can do math. You can calculate a break-even tipping cost for CO2 emissions on that basis if you like- it's pretty steep.

Algae to biodiesel? Again, at best a partial solution, with lots of technical obstacles that translate directly into economic obstacles. The only good thing I can say about algae are that most people wouldn't consider it to be food biomass, although "single cell protein" of various sorts has been pitched as an animal feed additive for many years. In terms of algae to biodiesel, just the cost to cover the required land area with glass or plastic containment structures resistant to weather throughout the year is going to be prohibitive, and open ponds give sharply limited productivity. The bugs don't make much use of increased light intensity, so there goes the plan to replace most of that glass with cheaper reflectors. Green plants solve this problem by growing their own support structures so they can make more use of the available insolation, but that comes with losses as well.

 

[cvg]

here's a good example, $17k capex per parking spot

https://cfo.asu.edu/solar-installations

Stadium Drive Parking Structure (PS 5) (provides 361 shaded parking spaces on top deck)

Max. Generating Capacity: 711 kWdc
Est. Annual Production year 1: 1,386,060 kWh
Actual Annual Production: 1,429,057 kWh
Capacity Factor: 28.68%
Commissioned Date: 12/2008
Number of Panels: 3510
Panel Size: 200/210 watts
Panel Type: Polycrystalline
Panel Manufacturer: Suntech
System Type: Single-Axis Tracker
System Installer: CarbonFree Technology
System Owner: Sun Devil Solar, LLC
Contract Type: Power Purchase/Qualified Management Agreement
REC Incentive: $0.25/kWh (APS)
Total Project Cost: $6,104,824

 

[TomDOT]

Oh, I agree that these structures aren't really practical yet (particularly as far north as Ontario!) Solar combination projects are effectively one-off "demo" projects at this point and nowhere near cost-effective.

And yes, the "crapton" calculation was joking, if cost were no object.

If you can point out a flaw or refinement in the Wal-Mart calculations, please go ahead. Obviously they were ballpark numbers. Commercial crystalline PV panels at the 18% efficiency level can be readily obtained. The best are more like 21% (unless you go stupidly expensive like the space-rated ones)

 

[cranky108]

Somewhere there was a statment that solar energy is at peak electrical usage. This is just wrong. At my location we can only expect about 6 hours of peak sun a day. The sholder hours are around 12% of that. A directional aming unit only add about 15% additional peak sun.
If peak sun is about noon, and is available 3 hours before that and after that, then how is that offset peak electrical usage at 6PM?

Wind has the same issue, it is highest at night.

What needs to be developed is an energy storage system that does much better than 50% losses.

As far as converting sunlight directly to chemical energy, I had these wall stick-ons that would do that, but they kept me up all night.

 

[TomDOT]

cranky - you're right, PV solar actually leads the peak demand. It's fairly close. Much closer than wind. Of course, since total grid-attached storage is pretty small (a few pumped hydro, one new kinetic facility) "close" doesn't help that much.

Thermal solar can be easily built with short-term storage (molten metal, hours in duration) to perfectly match peak demand. Cost is less attractive since PV prices dropped.

 

[patprimmer]

I thought a crapton was 1000 fart tonns which was a 1,000,000,000 truckloads.

Seriously I have been involved in two projects to replace existing materials in structures to have a double duty of collecting solar energy to be put to good use. Both failed, in my opinion due to failure to choose optimum design and materials.

One was a roof tile that substituted concrete tiles in sections of the roof of the home. It was a clear plastic and incorporated heating elements for a solar hot water system. It failed because the designer tried to use a fairly way out idea to mould a part in a 600 tonne press that should have been moulded in a 2000 tonne press and because being a toolmaker and used to working to 0.0001" accuracy at times, he completely failed to allow for the variations in dimensions of concrete roof tiles.

The other was a swimming pool fence incorporating a solar hot water system in the fence panels. It should have and still could work. The original material for the fence rails which doubled as manifolds or header tanks failed stagnation tests with chlorinated water inside after extended exposure when the daily maximum hit 40 deg C

An alternate material is chemically suitable but cannot be glued. They bailed out instead of altering the design to barbed socket like a light bulb fitting with O ring seals. I just may have someone else interested in buying the project from them.

Regards
Pat
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[cranky108]

Tom, it is because of this lead in solar energy that we need to keep existing power production. That we can't replace power plants with solar energy, until we develop more or better energy storage technology or methods.

There's nothing like buying energy for 0.10 $/kWh, and storing it to use latter, so the total cost is 0.15 $/kWh.

 

[TomDOT]

3 GW pumped-storage hydro:

http://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Station

...and on the cost issue: There's nothing like buying power at night for $0.05, and selling at peak for $0.50

 

[patprimmer]

Yep

Solar to pump water to store at an elevated position, then hydro from that storage pond seems a good realistic system.

Might even double up for irrigation mostly using existing infrastructure if the planners where real smart

Regards
Pat
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[cranky108]

Why not just use wind at night to fill that pond.

There again, look at how efficent it is. The losses are around 50%, water pumping is not efficent. Motors for pumping are not efficent. Hydro generators are efficent but not perfect. There are losses for evapration, and water flow in the pipe.
So take the expected energy need and use a 1.5 factor and get a better look at the numbers.

The reason pumped hydro is so uncommon is because of the need for height differences. That type of terain dosen't exist everywhere. And because of the cost of not only the plant, and lakes, but the difference in energy costs between day and night aren't great enough to justify the losses.