The Offshore Voyaging Reference Site

Solar Power

There are very few cruising boats that we see these days that don’t have a solar panel fitted somewhere, and many have some pretty substantial arrays. Our experience over the last five years has been largely positive, and we’re convinced that solar has played a valuable part in our supplementary power installation, wherever we have sailed, from the far north of Scotland to the Canaries. And with prices for larger panels now falling below $1/W, solar panels are becoming a more affordable option.


Login to continue reading (scroll down)

More Articles From Online Book: Electrical Systems For Cruising Boats:

  1. Why Most New-To-Us Boat Electrical Systems Must Be Rebuilt
  2. One Simple Law That Makes Electrical Systems Easy to Understand
  3. How Batteries Charge (Multiple Charging Sources Too)
  4. 5 Safety Tips For Working on Boat DC Electrical Systems
  5. 7 Checks To Stop Our DC Electrical System From Burning Our Boat
  6. Cruising Boat Electrical System Design, Part 1—Loads and Conservation
  7. Cruising Boat Electrical System Design, Part 2—Thinking About Systems
  8. Cruising Boat Electrical System Design, Part 3—Specifying Optimal Battery Bank Size
  9. Balancing Battery Bank and Solar Array Size
  10. The Danger of Voltage Drops From High Current (Amp) Loads
  11. Should Your Boat’s DC Electrical System Be 12 or 24 Volt?—Part 1
  12. Should Your Boat’s DC Electrical System Be 12 or 24 Volt?—Part 2
  13. Battery Bank Separation and Cross-Charging Best Practices
  14. Choosing & Installing Battery Switches
  15. Cross-Bank Battery Charging—Splitters and Relays
  16. Cross-Bank Battery Charging—DC/DC Chargers
  17. 10 Tips To Install An Alternator
  18. Stupid Alternator Regulators Get Smarter…Finally
  19. WakeSpeed WS500—Best Alternator Regulator for Lead Acid¹ and Lithium Batteries
  20. Smart Chargers Are Not That Smart
  21. Replacing Diesel-Generated Electricity With Renewables, Part 1—Loads and Options
  22. Replacing Diesel-Generated Electricity With Renewables, Part 2—Case Studies
  23. Efficient Generator-Based Electrical Systems For Yachts
  24. Battery Bank Size and Generator Run Time, A Case Study
  25. A Simple Way to Decide Between Lithium or Lead-Acid Batteries for a Cruising Boat
  26. Eight Steps to Get Ready For Lithium Batteries
  27. Why Lithium Battery Load Dumps Matter
  28. 8 Tips To Prevent Lithium Battery Black Outs
  29. Building a Seamanlike Lithium Battery System
  30. Lithium Batteries Buyer’s Guide—Part 1, BMS Requirements
  31. Lithium Batteries Buyer’s Guide—Part 2, Balancing and Monitoring
  32. Lithium Batteries Buyer’s Guide—Part 3, Current (Amps) Requirements and Optimal Voltage
  33. 11 Steps To Better Lead Acid Battery Life
  34. How Hard Can We Charge Our Lead-Acid Batteries?
  35. How Lead Acid Batteries Get Wrecked and What To Do About It
  36. Equalizing Batteries, The Reality
  37. Renewable Power
  38. Wind Generators
  39. Solar Power
  40. Watt & Sea Hydrogenerator Buyer’s Guide—Cost Performance
  41. Battery Monitors, Part 1—Which Type Is Right For You?
  42. Battery Monitors, Part 2—Recommended Unit
  43. Battery Monitors, Part 3—Calibration and Use
  44. Battery Containment—Part 1
63 Comments
Oldest
Newest
Inline Feedbacks
View all comments
Chris

We carry a 405 watt array. We are an all LED boat as well and use between 30 and 150 Ah a day depending on a myriad of things. On sunny days, using MPPT, we make back our overnight deficit in three hours after the sun gets about 20 degrees above the horizon. The deficit is made up while the daytime need is being met. This is true underway and at anchor. Except for air conditioning, the large water heater, and a succession of really dreary days, we have to invent reasons to run the genset. We expected payback in 4.5 years. Given fuel and electric costs in the Bahamas we got payback in less than two years.

Colin Speedie

Hi Chris

That’s a substantial array, and it’s good to hear what can be done. Food for thought for anyone who has the space to mount such an array, and isn’t sure whether they need a genset or not.

Best wishes

Colin

Torsten Hansen

Chris, I would love to see your installation but the links you provide are now locked as private by WordPress. FYI

John Harries

Hi Torsten,

Chris has not been cruising or appearing here for some years.

Dick Stevenson

Colin, This is a really nice report. Dick

Colin Speedie

Thanks, Dick – kind comments are always very welcome!

Glad you found it useful.

Best wishes

Colin

Alain Rémi

When can we expect sails with built in solar captors ? What’s the difference between the best solar captors (The one on the International Space Station, I assume) & the best -most efficient- we can buy today ? Thanks

Colin Speedie

Hi Alain

perhaps the day that such equipment is durable enough to withstand the flogging of a soft sail – I helped an ex RAF engineer with a project many years ago to develop radar reflective sails, and it was the difficulty in making it robust enough to take the pasting we give sails that was the drawback – nothing else.

Best wishes

Colin

Matt Marsh

A very nice, thorough summary, Colin, as we’ve come to expect from you.

One small correction. MPPTs – They adjust the voltage on both sides (battery and panel) to keep the panel operating at maximum V*I (not max V), near the ‘knee’ of its performance curve. If the panel is allowed to reach maximum voltage, it will provide no current and no power.

Also worth noting re. MPPTs – You can combine several panels onto one MPPT if they are of the same type and pointing the same way. Panel banks that are under different shading conditions or held at different angles should be on separate MPPTs. (I think we used six or eight MPPTs on the last solar car I worked on; the region beside the canopy, for example, would be in quite different light than the region near the nose.)

John Harries

Hi Matt,

Thanks for the correction of the error, which was made by AAC’s morphine soaked editor, not Colin.

Colin Speedie

Hi Matt, John

Fascinating stuff on MPPT, with some new angles that I hadn’t heard of before – make sense though, so thanks for the really useful explanation.

And no blame on the editor – who was only doing his best to clarify a point that I hadn’t made as well as I should.

Best to you both

Colin

paul shard

Thanks for your report!

On our first boat we installed 2 X 55W panels (15 years ago) and they helped out in the tropics, especially when we were in the Caribbean and Med. We had a rule never to sail north of 40 Degrees so didn’t try them in Scotland. But the past 2 seasons sailing the Baltic, Norway, Shetland, Scotland I am sure it would not have made much of a contribution. Perhaps we had rainier summers than normal 🙁

We do not have solar on the new boat (Southerly 49) and are still thinking about options. Although we have all LED lights (except nav lights) we still use about 200 ah per day at sea and I think we will still need the genset until solar gets a bit more efficient.

BTW – we have just arrived in the Graciosa, Canaries from Morocco – where are you?

Chris

Paul, it must be the clouds and rain.

The generally accepted panel angle for Islay on the Summer Solstice would be 27 deg; for Georgetown, Exuma on the Winter Solstice 23 deg – not a significant difference, nor a significant boost over a flat panel.

The insolation astronomically possible on Islay on the Summer Solstice is actually 84% greater than what is possible in Georgetown on the Winter Solstice.

Between June and July, Islay has had some of the cloudiest weather since February-March. Same with precipitation.

Colin Speedie

Hi Paul

With a substantial power daily power draw, a genset still makes sense. My view is that it is still worthwhile reducing (a) demand (as you’ve done, (b) supplementing with wind and solar to reduce (at least) use of the genset.

And there’s more to come – next part will be hydro power and new tech generation – and there are some really interesting new developments in that field that might be what you are looking for.

We’re in Puerto Calero getting ready to head out – perhaps tomorrow, if the wind goes off a little……

Best wishes

Colin

paul shard

Hi Colin,

Looks like we will miss you… we are in Rubicon heading off in a few hours for Las Palmas. We are going to film the ARC for our television show “Distant Shores”! We have crossed the Atlantic 4 times but never done the ARC. Should be good fun!

Best

Psul

Colin Speedie

Hi Paul

Sorry to have missed you – and good luck on the crossing!

Best wishes

Colin