How Much Solar

[OceanPlanet]

Originally Posted by belizesailor

See the spreadsheet link I posted earlier -- it will run the numbers for you and even project out across multiple days and show the deficit/surplus.

Also, the Isotherm (Danfoss compressor?) is likely to be more efficient than one of the portables (I assume that is the Engel you are referring too). Duty cycle should only be around 25%. Might have a fridge guy look at it and consider fixing the insulation problem.

Here's another solar needs worksheet, for boats....

[Azul]

Originally Posted by belizesailor

Good insight and especially relevant on a boat. Have not crunched these numbers, but let's see how it works out...
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This is by no means a statistically valid sample, but crunching the numbers on a sample of 4 panels from the Sun Electronics site (Solar Panels, PV Systems and Inverters Distributor) ranging from 105W to 315W the answer appears to be "GO BIG". More watts per Square Inch on the bigger wattage panels (also physically larger of course). On most cruising size boats a beast like the 315W panel, at about 65" x 52" could be a challenge to find a home for, but it has the highest watts/SqIn.

Next question to answer would be is there a difference between same wattage panels across brands?

Some of what I am going to say is going to be found to be stupid or controversial to the anal retentive "big thinkers" out there. You know who you are. I found almost no help trying to get started in solar on time and budget restraints so maybe this will help those of you out there that can't afford a $2000 system or 40 hours of pouring over charts, threads, 12V DC books etc.

Judging the total cost on the size of the panels be sure to include shipping. Panels over 145 W are too big for UPS and are shipped by freight which involves extra cost which is very significant in W/$. Also, it usually causes a lengthy shipping time. There is one exception I know of at least, the Grape 250W monocrystalline panel on Amazon.com (monocrystalline is generally preferable to polycrystalline for longevity and shading) which includes free shipping and yes these are Taiwan or Chinese panels that may only last 15 years instead of 25 or 50(the theoretical life of a monocrystalline panel.) Larger panels are usually not 12 V and will often require a more expensive charge controller and a little more thoughtful installation. For my system, (two 145 W DMSolar panels which fit perfectly on the last two arches of my bimini) I decided to buy a cheap HQRP PWM 20 amp controller for $47 which I can throw away if it is eventually inadequate or fails. I would have bought the Grape and a Morningstar Tristar 45 non MPPT as it is programmable for $170 but I couldn't wait on delivery. Total cost of system except batteries including MC4 25 foot cables and pigtail MC4 connectors was under $500 delivered in 2 days from Amazon.com. Two Group 29 WalMart deep cycle batteries with 3 year warranty $205. Buying a smaller wattage system will save almost no money compared to this as 50 W and 85 W single panels are usually $2 to $3 per watt. My loads? Whatever I can get to run off this. If I need more power I can buy another complete system for another $700, divided into two banks and have complete redundancy as well, or upgrade as needed or just pitch the whole kaboodle overboard for the price of a single 60A MPPT controller and for now I no longer have to worry about turning my non LED lights on or trying to start my engine with a dead battery. Next I plan to get a Trimetric 2020 battery monitor to guide the rest of my journey. (Proceeds to don fire retardant Nomex full suit...)

[willardj]

Originally Posted by Azul

Some of what I am going to say is going to be found to be stupid or controversial to the anal retentive "big thinkers" out there. You know who you are. I found almost no help trying to get started in solar on time and budget restraints so maybe this will help those of you out there that can't afford a $2000 system or 40 hours of pouring over charts, threads, 12V DC books etc.

Judging the total cost on the size of the panels be sure to include shipping. Panels over 145 W are too big for UPS and are shipped by freight which involves extra cost which is very significant in W/$. Also, it usually causes a lengthy shipping time. There is one exception I know of at least, the Grape 250W monocrystalline panel on Amazon.com (monocrystalline is generally preferable to polycrystalline for longevity and shading) which includes free shipping and yes these are Taiwan or Chinese panels that may only last 15 years instead of 25 or 50(the theoretical life of a monocrystalline panel.) Larger panels are usually not 12 V and will often require a more expensive charge controller and a little more thoughtful installation. For my system, (two 145 W DMSolar panels which fit perfectly on the last two arches of my bimini) I decided to buy a cheap HQRP PWM 20 amp controller for $47 which I can throw away if it is eventually inadequate or fails. I would have bought the Grape and a Morningstar Tristar 45 non MPPT as it is programmable for $170 but I couldn't wait on delivery. Total cost of system except batteries including MC4 25 foot cables and pigtail MC4 connectors was under $500 delivered in 2 days from Amazon.com. Two Group 29 WalMart deep cycle batteries with 3 year warranty $205. Buying a smaller wattage system will save almost no money compared to this as 50 W and 85 W single panels are usually $2 to $3 per watt. My loads? Whatever I can get to run off this. If I need more power I can buy another complete system for another $700, divided into two banks and have complete redundancy as well, or upgrade as needed or just pitch the whole kaboodle overboard for the price of a single 60A MPPT controller and for now I no longer have to worry about turning my non LED lights on or trying to start my engine with a dead battery. Next I plan to get a Trimetric 2020 battery monitor to guide the rest of my journey. (Proceeds to don fire retardant Nomex full suit...)

Your right. Most people can put a system together pretty cheap nowadays. 2-DM 145w(in series 10ga to mppt - parallel 6ga to pwm cc) are going for $320 to the house now. The Morningstar Tristar 45 pwm($170-180 with temp sensor) is a very good pwm controller you could run up to 4 of these panels with one. A few EGC2 6v 230ah batts from Sams going for $89 each so under $200 for 2 for a 12v system. A good batt monitor is a must too. That was the first thing I got before I even got my solar to make sure what the min I needed. As far as batt monitor I went with the Trimetric 2025 rv its smaller than the 2020 and can read 2 banks instead one(house n start batt it separate) and think it already has the lighting relief piece in it. If I'm not mistaken it was only $190 to the house for the monitor, shunt, and 30' of wire to hook shunt to monitor. So even if you get a super sweet monitor like the Trimetric you still only looking at something like only $900 or $700 w/o monitor. I think it is def a possibility for most people in today's times if they want it.

[Jimbo485]

From what I know now and with the current prices (yes, there has been a decent learning curve!), I would have more panels, a bigger inverter, and simply use 110 or 240 V domestic appliances, with the voltage depending on the country.

Instead of paying 4-figure prices for a fridge, you can put that same money into more panels and an inverter and buy a domestic fridge. The same goes for so much of the other crap which seems to accumulate on boats these days. The LED 54 cm flat screen for our navigation cost only $100, but had a 110V-18V transformer, so we threw it out and I hardwired in a $10 12V-18V transformer. Goes well with the $100 sextant which requires 0V but a decent sun shot!

Another example are our cockpit/deck speakers, which cost us US$15 but are 110V. So we use a simple US$20 inverter in the cockpit to run them. In fact, even though we now have a centralised 110V system, those $20 inverters, spread around the boat, seem to be the bees´ knees.

Of course, the marine experts will tell you otherwise and will want to sell you all the "marine" stuff where you basically add an extra zero to the price.

[noelex 77]

Originally Posted by Jimbo485

Instead of paying 4-figure prices for a fridge, you can put that same money into more panels and an inverter and buy a domestic fridge. .

As solar is getting cheaper, the most sensible set up is changing. For most boats the problem is that, even with the maximum number of panels that can be installed, running energy inefficient appliances is just not practical. Cats can fit more panels, but even here, many that cruise diverse places year around find they encounter areas where demand exceeds production, unless they fit the most efficient systems possible.

[Jimbo485]

QUOTE [many that cruise diverse places year around find they encounter areas where demand exceeds production, unless they fit the most efficient systems possible.]

Yes, efficiency is important, but when you put the $$ into your spreadsheet, it is quite easy to justify more energy supply via solar panels and forgo the electrical efficiency of the appliance. The exception is the high latitudes. We occasionally have more demand than supply during cloudy days or on a passage when the autopilot is working 24/7 and the sails are shading some panels.

So that is why we have one 210 W panel that is mobile and we simply place it where it is most receptive to the sunlight. But normally we are too lazy and it simply sits in one spot. When we anchor in the trades, the bow generally faces east and the sun is in the north, so the mobile panel is on the port deck. When on passage, we generally face more or less west, so the mobile panel is on the starboard deck.

Most people will not sit down and do the sums, so the qualitative debate is pretty irrelevant. But the maths is beautiful and does not lie.

With 20/20 hindsight I now realise we spent too much on LED lights. That money could have been better spent on another 600 W of panels, which in itself would have been excessive.

Yes, I was a nerdy engineer in a previous life.