The rendering above shows the proportions of a solar roof for the flying bridge (support is not yet shown, but will be required). The efficiency and cost per watt have gotten to the point where this may make sense. In the scheme above there would be eight 250 to 320 watt panels, depending on what we find next week. This is enough to generate a large chunk of our daily power usage at anchor. But is it worth the expense and hit on aesthetics?
Our approach to at anchor power has been working, and even with electric cooking, generator usage has been confined to evenings every second or third day, when the washing and drying were being done. Charging took place while we were powering, from the 150 amp Electrodyne alternators mounted on the engines. The 1600 amp hour battery bank would handle this for between three and five days, depending on the amount of computer time. Our eight kW genset was fine for the air con, and other AC loads, and when occasionally overwhelmed, would be assisted by the inverters adding the needed extra capacity.
But a couple of things have changed in the last year and a half. First, computer time has expanded and we are running a 27″ Imac with three external hard drives plus a second Mac at the same time. So, power consumption is up, now to 400 amps a day (at 24VDC). Second, we are sitting more and powering for shorter periods, which means the batteries are not being recharged as much by the engines. It has been necessary this year to run the generator a three hours every second or third day to keep the batteries feeling good. That in itself is acceptable. What is not is the dependence on this single piece of gear. We have the engines as a back up charging source, but we would not want to make a habit of using them this way.
Which brings us to the idea of solar panels. As the efficiency has increased and cost have come down they have become an interesting alternative. The issue is where to find the space required. In our case the roof of the pilot house makes an interesting possibility. The other potential location is an arch across the stern. Since we are working on a new awning and enclosure system for the pilot house, using the solar panels as a roof has merit.
There are three aspects to the decision. One is solar electrical production efficiency, a function of shading at various sun angles. A dense shadow line across a row of cells effectively shorts their output to zero. We are prepared to remove most of the antennae to facilitate output, but the radar and VHF need to remain.
The latest (beta) version of Rhino 3D has a shadow generator available without full rendering, so you can watch the shadows as the sun moves (or in this case the boat). The images above have six solar panels, but we are presently planning eight. This is a 1700 sun, from the stern quarter and directly aft. The radar antenna, all six feet (1.8m) of it, is in the worst position for shadowing. We are going to lose the better part of three panels in this situation.
Rotate the boat a few degrees and things get a lot better. Good friend and solar expert, Bob Williams, who is helping us with this, estimates that we will lose on average about ten to twelve percent of the total day’s output to shadowing. Lets assume 20% for fun. Using an MPPT controller increases output above panel ratings by 20 to 30%. We’ll call this gain and the shadowing loss even. We know we can source 250 watt panels (we are shooting for 320), so eight panels times 250 watts equals 2000 watts per hour. The solar day, i.e. average time of full output varies with latitude, time of year, and atmospherics. For temperate latitudes, we think we can assume 5.5 hours in normal climates. This works out to over 10,000 watt hours a day. To convert this to amp hours divide by your charging voltage, in our case 28, for 340 amp hours (for our 24 volt system) per day. This is between 70 and 90% of our daily consumption!
On the other hand, this is a large area in a potentially windy environment. The weight up high, an easy 250kg / 520 pounds, is way above the center of gravity so a knock on stability. Perhaps a five cell array on an arch aft makes more sense?
The decision will partly hinge on the new 320 watt panels and how soon we can get them. Stay tuned.
Posted by Steve Dashew (November 5, 2011)
November 5th, 2011 at 5:27 pm
On a much smaller scale I have been through the same thought processes. I found that there was a simple solution to the shade problem. Use semi-flexible amorphous panels. These are scorned by experts because they do not provide the highest output – in perfect conditions! However they tolerate slight shade, as you illustrate, or the boom of a mainsail. They are light weight and thin and fit the curved surface. You can walk on them, they are robust. Because they can tolerate slight shade, they also go on working early morning and late afternoon when the sun angle is lower, so any loss of efficiency is more than made up for by the longer working hours, and the MPPT controller makes this highly effective.
I tried this myself, and it works well on my boat, in not very sunny England. No I don’t have a commercial interest in it!
Cheers, Mike
November 6th, 2011 at 1:19 am
Hi Mike:
We’d love to use your system but the power density of the amorphous panels is not high enough for our needs.
November 5th, 2011 at 7:39 pm
Perhaps turn your solar array into moveable/fixed side awnings. Keeps the weight lower. More area? Are the booms good weight carriers? Combination boom solar array!
November 6th, 2011 at 1:32 am
Hi Paul:
We would love to use the solar panels as awnings but the output would be way down due to heavy shading.
November 6th, 2011 at 12:59 am
This is one of the few forums where legitimate questions about the overall efficiency of solar panels will not get shouted down by alternative energy enthusiasts.
My experience with a solar panels in a public art project in Portland eight years ago was that for the price of the solar panels and their associated electronics, hundreds of years of power could have been bought. I’m sure the panels and their associated equipment cost much less these days, but I’m certain that they will never pay for themselves for an installed application which never gets underway.
The very first ice storm after the solar panels were put up, the assembly failed and some very expensive replacements had to be made. While I’m sure the prices have come down, I’m not as certain that large installations are substantially more resistant to severe conditions. There is just so much area exposed to weather that they are statistically prone to failure. On as large an exposed surface as shown in the renderings, flex is going to become an issue sooner rather than later.
Cleanup is going to be a challenge, especially after a blow at sea. Factoring in the expense of additional fresh water, the effort of making sure they are clean, and the concern that the electrical assembly isn’t getting salted up is important. How well the panels respond to pressure washing compared to the awning is an open question.
Solar panels aren’t like diesels in that the accuracy of their endurance data is not an open book. As the failure of the Solyndra corporation showed, many of the institutions that should be auditing solar energy are too busy cheerleading to do the jobs they are supposed to. In ten or so years, there will be a lot more data that has been rigorously fact checked than is currently available. I’d be a lot more interested in solar as an energy source if there wasn’t so very much enthusiasm and so very little skepticism applied to it’s use. I’d want a lawyer to take a very close look at the contractual obligations of the panel manufacturer before purchasing them, which adds expense to their use. I have nasty suspicions that a lot of solar panels are only obligated to try to work.
Finally, like you stated, that’s a lot of expensive mass up very high on the vessel. I’m just wondering if the lower side awnings would be a better choice, especially because you wouldn’t plan on keeping them out in the weather very long at sea. You don’t need the power on the move, although they are never going to add to the Wind Horse’s look in port. The effort of hauling them in and out of storage would be a problem.
I really don’t like solar, and the more I see of it, the less I like it. My dislike is based on experience with solar in the field and discussions with installation professionals, as well as the inherent distrust that political enthusiasms deserve. There are too many people who expect to get something for nothing with solar solutions.
November 6th, 2011 at 1:29 am
Hi Patrick:
I tend to agree with you about alternate energy on land – hard to beat those diatoms who gave their all to create an energy source. But on a small vessel like ours, with the power density now available, the equation is different. We are familiar with the maintenance issues having had a large array on Sundeer back in the late 1980s. And we are particularly sensitive to it with this project. We very well could end up with a smaller but unshaded array on the stern. Lower CG on the mass, easier maintenance, and adequate output for our needs. The only problem aft is the panels overhang the edge of the hull slightly so are vulnerable if someone is coming alongside.
We have to decide early next week one way or the other.
Perhaps other folks with solar cruising experience will share what they have found?
November 6th, 2011 at 2:04 am
Fuel Cell Perhaps http://www.sfc.com/en/ – A little ethanol goes a long way.
November 6th, 2011 at 7:21 am
Racers used to install the glass-free IQSolar panels with great success. Very light, framed or frameless, and high power desity. Don’t know in which configuration they are available today.
November 6th, 2011 at 8:05 am
Hi Steve,
I have app 1.2kw worth of panels in 2 banks on a bimini top app 11′ x 17′, arranged in a U shape to avoid mast and radar shading. They’re controlled by Morningstar and Blue Sky MPPTs and charging a house bank of 1000 ah @ 24 volts C10. I’ve seen close to 40 amps @ 24 volts and can maintain a 20 gallon Isotherm water heater with a 750 watt element. My daily needs are not as high as yours. A good feature of solar is the fact that after bulk (genset) charging is done, they take over the float and absorbtion stages where burning diesel is inefficient.
November 6th, 2011 at 12:41 pm
Hi Bill:
Anything special about your hot water heater? Or, is it powered via an inverter?
November 6th, 2011 at 10:54 am
Have you looked at micro inverters? They are meant to localize shading loss to only the panels in the shade. That might be a workable solution.
–raj
November 6th, 2011 at 12:42 pm
Hi Raj:
We are not familiar with micro inverters. More info would be welcome.
November 6th, 2011 at 11:57 am
Steve,
In some ways I hope you get at least one panel and do your customary thorough analysis of the costs and benefits of the panel. I respect your “breath integrity”, where your bona fide’s are inherent in your willingness to test your designs in life threatening situations, much more than I do the speculations of people angling to receive subsidies for abstractions. I suspect that solar is still not good enough to merit the expense and effort, but I wouldn’t mind being proven wrong by somebody I trust to be transparent and acknowledge failure.
I suggest that the rig would make more sense as an in-port battery stretcher that could be struck at sea and during heavy weather in port. My biggest systems engineering concern about solar is the replacement cost and failure rate in harsh environments. My biggest social engineering concern about solar is the widespread fraud regarding costs and benefits. I’d really love to see your numbers compared to a comparable mass of additional batteries.
Also, how much of your “hotel” lighting is LED? There may be some energy savings to be gotten from a transition to different lighting that would reduce the need for additional generation.
November 6th, 2011 at 12:54 pm
Hi Patrick:
There is lots of real world experience in the marine world that validates the efficacy of solar power on cruising yachts, and main stream panel producer product stands up well. The private sector has no problem competing with foreign subsidized suppliers in terms of quality and efficiency. There are also lots of off the grid homes that run on solar at lower cost than bringing power to their remote locations. So, don’t condemn the entire concept because of Washington corruption. Note that I am referring to off the grid situations.
In our case, the solar array acts as a back up to the genset, and reduces or eliminates the need (most of the time) for the genset to provide power f or charging batteries, which n turn makes a smaller genset possible.
LED lightning is not yet where it needs to be in terms of warmth (color wise) and dimming. We keep looking and testing. Maybe in the next year. Keep in mind that lighting is a small part of our total consumption
November 6th, 2011 at 12:15 pm
Hi Steve
Why not just mount them around the upper pilot house on the roof of the great room. PV cells are heavy (with support) and the connections low voltage so you need to get them!
Trevor
November 6th, 2011 at 12:55 pm
Hello Trevor:
There is not enough space on the house roof forward of the flying bridge, and it is shaded to a much greater extent.
November 6th, 2011 at 1:03 pm
Solar’s certainly a lot cheaper than it used to be. (10 kW class systems are now about $60k installed, or $6/watt, on land here in Ontario, down almost 40% from just two years ago.)
It’s also a lot more reliable than it used to be. All the reputable dealers around here now guarantee the panels for 20+ years. That warranty usually covers slow degradation to less than 80% or 90% of rated output. You can get cheap crap elsewhere, of course, but the big names here do stand behind their products.
The 2.0 kW array you’re describing for the FPB is roughly comparable to what we used on the two-seat solar cars Gemini and Ultraviolet. If you want to keep costs reasonable, then yes, go with commercial modules and it’ll be a bit heavy. If money is no object, an array that size laminated with SunKat ($$$) or Gochermann ($$$$$$) encapsulation is only 2-3 mm thick, could be glued to a Kevlar honeycomb panel, and is light enough for two people to carry around.
Careful arrangement of the MPPTs makes a huge difference. One MPPT for the whole bank will be disappointing. Several small MPPTs, connected so that each one’s panels are subject to roughly uniform illumination/shading, work far better. (A typical solar car has three to eight MPPTs, and the elect team frets over simulations for many days, figuring out how best to connect them.)
November 6th, 2011 at 1:09 pm
Steve, my water heater is run off my 2 x Victron 24V 3000watt inverters as are all AC loads. The solar banks usually catch up with the water heater by 1300 hrs or earlier; the rest of the day tops off the house bank. I run a small, 750watt Victron inverter for the computers and shut down the big ones to eliminate their standby loads.
My “genset” is a 24V battery charger, a small Kubota diesel pulling a large 24V alternator with Balmar regulator putting the charge right into the house bank.
November 6th, 2011 at 1:29 pm
Steve,
My problem with most “off the grid” claims that have come to my attention is the focus on generation methods and scarcity of data relating to cost and quality of life. The absence of discussion in major media of failures caused by alternative generation sources rings my alarm bells. Every technology fails, and when people get religiously invested in the technology, the reporting of failure is not accurate, timely, or coherent. Some of those small windmills and solar rigs had to have failed, and the lack of failure analysis does nothing to make me trust them. Some of that is governmental funding’s natural dampening on transparency, but a lot of it smells like “something for nothing” enthusiasm getting in the way of measurable progress.
There is a Sylvania battery driven LED lamp I got at Lowe’s last week that meets a pretty exacting standard of warmth. That LED not available in either 12VDC or 110/220 VAC in a product I’ve seen yet. I’m 80% sure this is the light, although I purchased it in a single light package. http://www.lowes.com/pd_166184-3-36098_0__?Ntt=LED+Dot+It+&UserSearch=LED+Dot+It+&productId=1217271&N=0
There are still some fairly substantial holes in most “white” LEDs, but a friend of mine put together a fairly true light reproduction for stamp collectors some years ago. He relied on UV tubes for “serious” far-UV, but could do a reasonable recreation of white and most other colors. There is a patent block where combining three LEDs to create colors was an unavailable technology without serious license fees, but he used two LEDs to do a very good simulation of most hues.
LED technology is a lot closer to price/performance/quality every year, it follows Moore’s Law pretty closely.
November 6th, 2011 at 1:56 pm
Basically, Micro Inverters are small inverters placed under each panel. The biggest selling point is that if one panel is shaded it does not affect the output of the other panels. The claim is that overall output is better from the same size of solar array.
You can read a little bit about micro inverters here.
http://en.wikipedia.org/wiki/Photovoltaic_micro-inverter
Enphase is the most common name in micro inverters. Here is a link to their site
http://enphase.com/products/microinverters/
–Raj
November 6th, 2011 at 10:58 pm
Hi Steve … And what about the foredeck? You seem to have some “real estate” there, both on top of the coamings and also in between them. Best Regards, Alex
November 7th, 2011 at 7:44 am
Hi Alex:
The foredeck area it too small once you leave walkways, and typically covered with an awning.
November 7th, 2011 at 2:35 am
Steve, I’ve been thinking about your solar concept …
From a purely engineering/cost standpoint, I’d skip the solar awning, stick with a conventional Sunbrella type for shade, and attach solar panels to the ample open surfaces you have available on the boat.
If you wanted maximum efficiency at all times from the panels you would need an active mount to orient the panels at all times; this often costs far more than the panels themselves and introduces yet another point of unreliability into the system. Wind/current reorientation of the boat requires panel repositioning, for which power isn’t free either.
I’ve investigated such systems; it’s often far more economically efficient to mount an excess of panels on multiple angled surfaces and accept what the exposure angles provide based on how current/wind conditions affect the orientation of the boat. You’ll have far fewer points of failure in the system and a more consistent output regardless of angle without requiring active mechanical intervention. Panels are relatively cheap and reliable. Active mechanical control systems are neither.
Summary: install high-quality panels, maximize surface area, control them well electrically (operating point optimization, not reposition them) and be done with it. Don’t mess with active mounts, extra structural engineering and the Pirates of the Caribbean 😉
An operating point optimization would help increase overall yield far more than any sort of mechanical manipulation.
One more point:
A number of years ago we bareboated a Maine Cat 30 in the Abacos; with a well-exposed (I think) 200W of panels it took fine care of our refrigeration, night time ventilation fans, VHF, and a well-used audio system with no assist from the alternators on the outboards, as we didn’t use them. NIce.
Mike
November 7th, 2011 at 8:32 am
Hi Again, Mike:
From our own experience over the years we agree 100%. In fact, after working through the fly bridge roof details we are back to fabric. We have an alternate plan for the solar panels that we’ll share as soon as we have some drawings finished.
November 7th, 2011 at 12:07 pm
Steve,
An interesting solar installation can be found at http://lerevereport.blogspot.com/2011/06/solar-panels-installed.html and http://lerevereport.blogspot.com/2011/06/more-solar-panel-pict.html. Solar panel tracker… We are definitely seeing some innovative ideas for displaying solar arrays! Enphase Micro Inverters as well as Nanosolar’s Thin Film Printing Technology now competitive with crystalline silicon panel efficiencies, are both excellent ideas. Anything that can reduce the overall carbon footprint, I’m sure, will be well embraced by the marine community.
Good Luck!
November 8th, 2011 at 1:34 am
Scott M.,
Pardon me for saying this, but I find it difficult to believe that the Sheiks on giant yachts in the Med, the guys with super-fast cigarette boats, the sponsors of the America’s Cup series contenders, or the celebrities flying to Oslo on private jets to environmental conferences care even a little bit about their carbon footprints. The marine community is vast and diverse and their concerns an motivations are often antithetical to each other’s.
Steve is posing an interesting technical question about the costs and benefits of solar supplement to his generator. Thin-film has shown itself to be a flawed and cost ineffective solution, which is one reason why Solyndra went bankrupt. Above, Mike detailed some of the key reasons why tracking solar systems are essentially compromised for maritime solutions.
One of the key reasons why solar and other alternative solutions are viewed with suspicion by a lot of people who’ve had to deliver engineered product according to specifications is the volume of the cheerleading compared to the accuracy of the benefits delivered.
My family hosted the first Earth Marchers in our house in Lake View Terrace, California for three days in 1970. The Earth Marchers left our pool a toxic wasteland, overflowed our septic tank, and proceeded to show similar results around the world in the forty-one years since. I really like the environment, but it’s fan club is a disgrace.
November 8th, 2011 at 6:46 am
Howdy Patrick:
Bob Williams at SALT in Marathon, Florida,has been able to get some of the new 19% efficient 320 watt panels for us.We have some firm numbers on output which we’ll share when we write up a few notes on the design in the next day or two. The six panels will generate more power than we normally in most normal cruising environments, so we are fitting an electric hot water heater to absorb the excess capacity. We’ll know soon enough if the claims for these panels are true.
November 9th, 2011 at 1:34 am
Steve,
When a buddy of mine and I were doing some early LED flashlight conversions and other LED projects, there wasn’t a meaningful standard test of brightness. Since claims of brightness measured in candlepower are frankly fraudulent for directional lighting (candlepower is measured in spherical output), we put together a rig to test how bright our lights were. It used a black painted PVC tube one foot long with a lightmeter on one end and a flashlight at the other. When we rigged continuous power to the lightmeter, we could test for as long as needed. One early test showed that we could get useful light out of two AA batteries and a 2002 vintage LED for a month.
A similar rig that would block light to a solar panel and allow a measured quantity over a known area of light should give you pretty good measurement of solar panel deterioration over time. Using LEDs, rated for 100,000 hours of life, a minute at a time would provide a good source. You could also just get a light meter rated for solar exposure and hang that out on deck as a fixed installation, but I am less sanguine about the endurance of calibration equipment left in the sun and weather.
Another concern I have, which I’m sure you’ve considered, is the dark sides of the panels. Dark places in moist environments are a natural habitat for “Bad Things”. I’m less worried about mildew, moss, insects, jetsam, and critters than salt buildup. Based on the renderings, it looks like there will be a hard to reach area between the panels and the awning.
Thank you for your tremendous patience on answering concerns on this project. To the extent that this solution can be made workable, I’m certain that you can do it and have the integrity to admit that something doesn’t work if it fails.
November 9th, 2011 at 1:06 pm
Just as a comment… module performance is very dependent on how the shade is oriented. It’s possible that shading only 6 cells can nuke a crystalline modules output, while shading 12 cells along a different alignment might only kill a 1/3rd of the output. Longevity of the modules is excellent. Weight is a valid concern.
Thin film is not as severely impacted by shading as the internal structure tends to be wired in parallel instead of series. There are some other thin film products available that are not a-Si. The CIGS technology is showing promise, with module efficiency around 12%. Products are available in flexible form. Longevity is unknown because it’s very difficult to to performance life cycle testing on photovoltaics.
Micro-inverters are not an option. They’re designed to run in a grid-tied configuration only.
Brian
Solar Design Engineer and Trainer
NABCEP Certified PV Installer
Solar Geek
November 9th, 2011 at 1:07 pm
It is also true that PV panels block/absorb radiant heat which gives them a serendipity–where it is sunny and nice for PV is is likely hot in that sun and reducing hull-heating would be useful. A solar array is like a portable tree canopy in that sense. Perhaps the fore-deck or side deck awnings could be replaced with PV panels?
November 9th, 2011 at 10:24 pm
Howdy Mr. Jones:
The foredeck would be great if not for shading by the house and fly bridge awning. We have a new location, to be revealed as soon as there is a spare minute to write it up.
November 24th, 2011 at 9:29 pm
Steve,
Here is an interesting article on research at MIT on 3D photovoltaics. It shows the inefficiency of using flat PV panels.
http://zeppola.mit.edu/pubs/APPLAB967071902_1.pdf
November 30th, 2011 at 10:30 am
Scott,
Arguably the new panels won’t be flat, they’ll be wave formed. The inclination of the panels at any given moment is more a matter of probability than static systems efficiencies would predict. As much as I dislike solar as a religion, I respect Steve’s gamble as a shrewd one.
February 25th, 2012 at 4:17 am
If something like this had tracking you might get by with fewer panels. Stow when underway.
Kinda has a “James Bond” look but form follows function. Wind turbine may provide another/additional source.
http://www.solarstik.com/products-solutions/marine-systems-accessories/marine-solar-stiktm-100-deck-mount-system
Also curious if you researched concentrated solar?
February 26th, 2012 at 1:29 am
We’ve looked at trackers over the ears, but always come to the conclusion that they were too complex for our environment. We have not looked at solar collectors, yet.