Portable Solar
I just got off the phone with a manager of construction projects who has used a portable array of solar panels and a small wind turbine with battery storage to power his sites before grid electricity can be brought in, implemented as a replacement for gasoline generators. He says, quite correctly, that this solution is appealing to those interested in supporting the migration from fossil fuels to renewable energy.
That said, I’m not bullish on this for a number of reasons:
• First, a minor point: the wind generator will produce very little at ground level in the typical construction site; the device would be more cost-effective without it.
• More importantly, while there are people who care about our environment (fortunately), the primary driver of decisions in the construction industry is dollars and cents, and there is no way that this device is going to compete with the 33 KWhs that are available in a gallon of gasoline.
• This device needs to be sized according to the predicted load.
• The small footprint of gas generators is another advantage.
• The ease of portability of gas generators is yet another significant advantage. This needs its own chassis that needs to be road-worthy and government approved.
Needless to say, I’ve seen more than my share of devices like this at shows like Solar Power International and Intersolar. In my mind, it’s a concept with no future.
Of course, permanently installed solar and wind on a decent scale are becoming more important to our world every day.
I beg to differ on some points above.
Re the wind turbine, I agree with you this has no useful place on a building site.
Re energy content of gasoline, whilst there is around 33kWh of energy in a gallon of gasoline, you would be lucky to extract more than 10kWh as electricity. Cost wise, whilst gasoline is cheep in the USA, in Europe it is not. By the time you have paid for servicing, in Europe, you would not have much change out of $1 per kWh.
I would see a niche market for portable off grid systems – especially where low noise levels, and avoidance of pollution is at a premium on smaller sites.
I would however consider a hacked Tesla Powerwall, or second use electric vehicle battery – set up to recharge overnight in the workshop, and power hand tools and lights on site by day. This could be linked to a small optional solar array to extend time between charges.
Great points. Thanks.
Great points. Thanks.
Craig,
Well said. This is another innovation with very little value. Sort of like the concept of towing a generator behind an EV.
A few years ago I was asked to evaluate a similar, (but better built) unit designed for agricultural use. The unit had some merit as it could be transported from location to location easily and could operate without maintenance, or a store of diesel.
Unfortunately, when batteries were added the weight, cost and inconvenience made the unit unattractive.
However, portable illuminated solar road traffic signs are in wide spread usage, so it’s reasonable to conclude that more specialist applications of this sort of device may be developed.
I actually once considered the idea of a genset trailer for EV a rather good idea and not really different than carrying extra gasoline when going on a trip to the wilds. It would be far more efficient and less costly overall, socially than constantly carrying around a much larger battery than is actually needed or building a network of charging stations that might be little used out in the country.
The best potential would be as a rental. Variations of this are “pusher trailers” and solar trailers. At some point however energy storage becomes cheap enough to overcome the trouble this would necessitate. I am not sure we are there yet. Perhaps this is the most well documented genset trailer for an EV: http://www.evnut.com/rav_longranger.htm But there are more modern variations: http://newatlas.com/ev-charging-trailer/28513/
Presently commercial electric cars are designed to stop charging if they are moving as a safety measure.
In this it is similar to the idea of zip cars or sharing a vehicle between several owners. The capital is used more efficiently with less expense.
The sad fact is that it then requires more social organization and dealing with other people in a cooperative way is a strain for some people.
Breath,
EV’s are constantly re-charging from regenerative braking.
Marco, it is true that at least a commercial EV will constantly recharge from regenerative braking. But I constantly get questions from someone asking why this does not lead to a perpetual motion machine.
While there are a number of ways to consider this one way is to make a distinction between the energy in stored fuel, sunlight or that can be transmitted to the vehicle from outside of the system and the energy that is only recovered that would otherwise have been part of wasted energy within the system.
Like extra fuel to an ICE all the trailer systems like charging stations add additional energy to the EV while regenerative braking is essentially a conservation device.
Sorry Marco, I now get your point. To clarify, a commercial EV is designed to disconnect the charge point on the vehicle if the vehicle is moving. This certainly makes sense as it is presently expected that the charge point will not be moving with the vehicle.
Yes it might be possible to engineer an attachment from a genset trailer to a different part of the system. However if someone wanted to simply pick up a rented trailer for a long distance trip with your EV, being able to attach to the normal charge point could be an advantage as would having the charge point at the rear of the vehicle.
Coincidentally, I did a market research project for a developer of a generator that could be rented by the day and towed behind a battery EV, turning it into a plug-in hybrid for an occasional long trip. I didn’t think it was an unreasonable idea, but I concluded (via asking a few hundred relevant people) that it would be a tough products sell.
Craig, No doubt this is one of the reasons that a top down distribution of goods has some problems. It sometimes takes a bit of education to help people understand the benefits of a product or system. This adds cost to the overall product.
But it would be interesting to see advertising that is informative and educational and not primarily based upon sex appeal. But that is an alternative universe.
Craig, I once crunched some basic numbers on the cost of electricity from a portable generator. The relevant facts are the cost of gasoline and the fuel usage of the generator. With gasoline above $3.00 a gallon I came up with a typical $.75 per KWH basic cost to produce electricity from gasoline. Now the cost would be slightly less.
Additional cost factors for a more complete (and larger) number would have to consider the cost of the generator and maintenance on the generator.
The cost of a trailer would have to be added to the absolute figures but is matched by the same for solar panels. Many construction projects use a box vehicle or trailer as a temporary workshop. Alternatively, or larger projects there is a mobile site office and solar panels could be attached to these to avoid the separate cost and storage space of a separate trailer.
I would be very interested in the cost of the solar panel option if you, the contractor, or someone else wanted to take an interest in suggesting some numbers.
I have seen several ways to make a wind generator of used parts and I think this self made approach may be reasonably cost effective as it would reduce the initial cost. Otherwise, I can think of several instances where the cost effectiveness of a wind generator will not be the most important consideration. It is part of construction and other fields to sometimes work on the basis of “getting the job done.” You can’t tap into a wind resource with solar panels or a generator.
Of course, a temporary service drop would always be preferred, but renewable energy may be a strong selling point to a prospective customer if you can advertise the renewable nature of your construction energy resource. Over the course of a larger project the additional cost (if any) of renewable energy may be a nominal expense relative to material and labor and may be more than offset by an increase in prestige or desirability.
So while I appreciate your brutally honest concerns about the contractor’s bottom line and your wanting to clear away the smoke and mirrors, when you consider that the manager specifically mentioned the appeal to some specific customers this context is likely an important factor, and a whiff of smoke may not necessarily be a harmful thing. This is especially true if it makes the difference between selling a job or losing it.
Breath,
You make a valid point with the “green” appeal of such a unit.
However, it’s very difficult to compete with the tax deductible cost of a 6kVA at 50Hz, 12HP 4 stroke diesel generator, with a noise level of only 70db at 7m 4 gallon fuel capacity, 8 hour running time per tank. Weight: 125kg: Size, 920mm (L) x 520mm (W) x 740mm (H).
This unit costs less than $1200, or can be hired. The unit operates all year ’round, day or night, indoors or outdoors, can increase or decrease load.
I can see some possible specialist applications for portable solar, but for general use, Craig’s right, it’s hard to beat the convenience of diesel.
Yes, Marco, this is my being in conflict. While I hate the idea of inefficiency and cost ineffectiveness there are also sales considerations. And it could be a plus if the contractor says to the client, “I know it is more expensive to do it this way but it’s because I care… just as I will spare no expense to give you the home you want.” Wow! That is the contractor the future home owner wants isn’t it? Now the same line might not work so well for a commercial customer.
And if we then find ourselves living in a world where we spend a little more because we care, is that such a bad thing?
Breath,
I agree, and I wish there were more environmentally aware clients. A world where we spend a little more because we care would be a very good thing indeed !
While diesel generators are certainly better adapted for such constant load stationary applications they are far less common in the US. Virtually everything you will get from a big box store here is going to be gasoline.
Although I didn’t mention it previously the cost of acquiring and storing fuel is not a small issue. Especially as on a smaller basis like this labor will be a factor when you are not simply scheduling fuel deliveries for your generator.
By the time you get into power demands more serious than hand tools or a few shop tools … something that would require a larger diesel generator you are not going to replace that requirement with four solar panels and a few batteries.
But more recently I have seen some highway lighting equipment which has substituted a generator trailer and light set up with solar panels, batteries and low demand lighting.
In a general sense everyone’s concern over cost effectiveness versus traditional diesel or gasoline generators can make these attempts of portable green power like you describe more of a nice concept than a real viable solution. But not absolutely.
However, Breath’s last Post illustrates how things though are changing and serious companies have begun deploying more and more of these small to need solar / battery / low wattage lighting units and they work quite well and are gaining more acceptance.
Hells bells new Railroad Hopper cars have small solar panels on them 2 to 4 to a car for heaters and also for motors to release hopper doors. More growth in Niche applications for Solar!
This is happening because the price for good wattage and performing solar modules ready to go is in the $ 1.00 to 1.20 per watt . Add $ .80 cents or less a watt for inverters, racking / supports/ mounting to the top of construction trailers as a high estimate or cap price.
So $ 2.00 per watt with a .88 to .90 derate factor so 30 year efficiency is good. 25 year life on Invert-er. Or you just may run the whole thing on DC , order customized lights that are DC. No need for an inverter. You will size these systems to meet the loads. but use $2.00 Watt total installed price and that is HIGH estimate. Includes all racks , tubes, clamps mounting hardware for the mobile deployment.
Now you get creative in how you design and construct these mobile units. I will call this a hybrid mobile design. This design is to power more than just a few lights it will operate lots of power tools and office computers , etc.
You can run power cables to different light stands and avoid light trailers altogether.
You will have to be able to visualize as I can’t draw this in Craig’s word space.
So we are going to leverage some things ( construction trailers) to gain embedded economic advantage and in the process lower the cost to use green power and save Fuel costs and Save fuel for the heavy equipment rather than burn it to make lighting power or safety signage power tools small ones. Make the office /storage trailers become power generators and use some wiring cables to distribute the power as needed.
1. We first are going to use a lets say 5 Kw to 6 kw (5,000 to 6,000 ) watts array that is about 25 feet long. This will fit on the roof of a traditional construction site trailer they are 8 to 10 feet wide and 20 to 30 feet long. Bear in mind that most construction sites will have one or more of these trailers at a site. They are used for mobile offices , store tools , cook food, etc.
2. The solar design is unique in that we use a WASH Board design that one panel having a western orientation at 15 degrees slope, opposite one facing East at 22 degrees. repeat this build out to 25 feet or so. The array looks like some V V V V ‘s) these panels are close to 400 or 450 watts each. ( they have have come a long long way from the 180 watts of 10 years ago. Increased Power Density.
1a. One manufacture is delivering a 500 watt panel 2nd qtr this year. Note these are not bifacial panels but standard poly or mono design panels modules.
2a. The EAST WEST design delivers typically 7 more watts per sq ft than traditional South facing panels. This increased power density in the aggregate makes a big difference from a systems perspective. In commercial rooftop applications this design delivers 59 to 60 more kw than a traditional South ( only) facing array on a 10,000 sq ft rooftop. Or on the ground it would be the same increase of power density. However the advantage of using the mounting on the trailer roof above the ground level would result in more cooling for the panels and reduce heat losses. 6 to 7 % more power output.
3. Now visualize 2 more arrays each same Washboard design ( a V V V V V V V V array ) the same length and they are inserted into the V on top of the first one ( stacked) . This is for shipment.
4. Once at the site – some tubular metal support system allows for sliding the top array to the left and the middle array goes to the right so now the trailer has the center array with an array extended on both sides. Slide down support poles can be extended to the ground to support and stabilize the solar array.
You also have a shade feature for workers to eat their food under. So we are creating a more positive work environment as well.
5. Ground mount design for certain sites can be used over the Trailer. But since you are going to take a trailer to the site for large projects anyway leverage it. These WASH board lightweight systems can use small ballast bricks to make them steady and wind proof etc. Simple part.
6. Now going back to the trailer picture that Craig first started out with , one would carry a series of V ‘s stacked on top of each other or nested as they say and you can just use a few mobile light trailers that they are going to have to tow anyways.
So I take the contrarian view and say the use of solar for these types of applications is not just a Nice Concept but another advance in the usage of Green energy. You get more power so you can store more power in batteries and reduce the need for fossil fuel. LED s use 75 % less power typically , so this reduces the solar scale and battery requirements also.
Craig the small wind feature tends to make this like Marco said a interesting concept but not too practical as its hard to get more than 10 kw in small wind designs . Small wind generators have high bearing failure rates etc., more trouble than worth. One needs to have a tower height of at least 35 Ft or even 50 ft. to capture measurable and usable wind power. so it is usually impractical and may not be necessary as the solar panels are now more powerful in wattage . The small wind part is the Green Bling aspect – impractical.
So on the surface one could say that mobile solar light trailers may not be practical but I would encourage you to take a deeper look beyond the Tip of the Iceberg Mates!
The construction industry is using more and more of the small trailers with a few solar panel systems along the highways each year.
The economics could be quite positive due to low solar costs, zero fuel costs reduced life cycle costs because of less maintenance costs versus a generator. The reduced need or size of fuel loads etc. , is All Avoided.
The capacity factor of these systems is also higher, tends to be in the 26 % to 28 % range versus conventional South facing solar. Delivers stronger performance in summer months longer running time so less need for batteries.
Solar at 22 % site efficiency can outperform diesel fuel generators at 33 to 37 % burning efficiency due to extremely Low life cycle ownership and maintenance costs and eventual rising of Diesel costs. Air permitting issues related to a construction project are reduced and if there ever is a carbon tax the savings stack just accrues greater.
Trust this sheds a different perspective on Craig’s post.
@ Craig and Breath
here are some Kwhr cost figures for the innovative solar system that I described in my post.it was quite late last nite and wanted to make sure I got accurate figures to show that certain types of portable solar systems can be quite cost effective and change onsite construction or road work projects energy usage.
We can get away from Carbon fuel systems if we get creative.
sizing a 6.1 kw system like I described would generate 14,000 or so Kwhrs annually if used every day. since we are sizing for a project to project basis I break it down into a daily production capability of 38.3 kwhr a day out put. Plenty to run banks of lites . Want more add panels.
1 6.1 kw array would fit on a construction trailer or even a small portable trailer like in Craigs picture.
The LCOE – levelized cost of these Kwhrs over 30 years with the 30 % tax credit would be $ 0.04373 per Kwhr
The LCOE – levelized cost of these Kwhr s with out the 30 5 tax credit is $0.06248 per Kwhr.
Also this eliminates Demand charges ( $ 20 per kw ) if you did a portable Grid power hook up plus the fees related. A complete cost / savings stack analysis would reveal that the portable solar could be economically attractive.
This 100 % below the average cost of electricity from the Grid in the SW United States so solar systems are more than cost effective if the entire supply chain and O & M cost and fuel cost are properly accounted for.
Years ago the Holy grail was grid parity well we are way below Grid prices now.
One last thing on this portable power concept – both the British and the American Army have used portable power in solar formats for base camps and troops to generate power for electronics and run the camps to reduce fuel supply chain costs and tactical vulnerabilities. typically they use flexible solar panels that hang from tents and trucks and the like. Not real efficient but in the aggregate they can scale up and it reduces the supply chain costs and the fuel needed , etc. Tactically a good move safer deployments.
In certain areas in Afghanistan , the British Army has some what I call Pop up Wind turbines that are small and mounted on Poles that go up 35 feet or so above , they only work in good wind areas.
While they worked they did make for a Good target for the Taliban fighters ! But that is in a fighting zone.
During a Solar plant scoping mission at Magregor Range – Fort Bliss in 2011 I saw these systems on a tour of the base in So NM. The wind turbines were 3 kw in size and the Army company had around 100 kw of flexible solar panels being used. Both the American and British information officers said they were a new tool in the tool box for modern mobile fighting forces and Greener military operations.
So Craig not so far fetched!
So it can be done.
Consider the case of a large company regularly installing solar rooftop arrays on houses / commercial new build as part of the construction process.
All hardware is available wholesale, and installation is by their own hourly paid workers.
Consider a 6 kw array with a Tesla Powerwall 2.
Solar panel costs ex factory 31 to 41 cents per watt – call it 50 cents delivered.
6 kw of panels net of tax $3000
Tesla Powerwall 2 $5500 + delivery.
Other hardware – rails, clips, cables, breakers etc. $ 500
Wages $ 500
All in installed cost around $10,000.
As it is off grid and temporary, no planning permission or grid connection permit needed, and probably no inspection required.
For a builder / developer this system could cost less than the installed cost of a 6 kw system retail on grid without energy storage!
Gary, thanks for running the numbers. You present a bit of a special case but that doesn’t make it any less valid. Rather I think it shows that no matter how we analyze things with averages and generalities there are always specific circumstances.
We might say something doesn’t generally make economic sense and then someone with narrow circumstances takes another look and makes it work.
Just sometimes this might then provide experience to make our innovation generally economical.
Good work.
I meant to say installed on temporary site buildings I.e. portacabin office.
@ Gary
yes your costs make sense and show that the earlier dismissive comments about portable soalr were wrong. It does not cost that much.
I was using $2.00 watt to be conservative pricing a complete system all in w financing costs built in also.
so we both are showing the emerging practicality of using portable green power.
the times are a changing in right direction ….of course as long as close minded carbon heads conspirators don’t get in the way …like they are trying to do in America right now.
Hey Craig,
Thanks for posting this.
I see lots of interesting comments!