Gulf Island Off-Grid System

David and Laura · March 2011

Greetings!

My wife and I have been researching various options for building an off-grid solar power system for a home that we will be building on a Gulf Island in British Columbia, Canada. We're designing everything in our home to reduce the amount of electrical load that will be required, but we've got a couple of wrinkles that make this a little different from a typical textbook design...

The good:

1) We have some good bluffs where we could install our solar panels to get an optimal south-facing view.
2) We have approx. 2 - 3 KW of micro-hydro potential in the winter months, which coincides with when we get the least sun and the most clouds/storms.

The bad:

1) No grid. No chance at getting any form of connection.
2) We're going to need to run some communication relay equipment on a tower that will consume 12 KWHours per day. (ouch!)
3) The location where we can site the micro-hydro, where we can site the solar panels with a south-facing view, where our house will be located, and where the tower will be located are 500 metres to 1000 metres apart.

We've inherited some equipment, namely a 24 battery single string of Deka Unigy II batteries, and a Alize 8000 SDE diesel generator, and we've been considering the following additional components:

1. Kyocera KD235GX 235Watt panels (24 - 30 panels, on two or three strings depending on how the voltages and amperages work out)
2. Schneider/Xantrex XW-MPPT60 Charge Controller (1 or 2 depending on the system size)
3. Schneider/Xantrex XW6048 Inverter (or 2 XW4548-120, depending on system size)

Given that we're going to be looking at a combination of solar and micro-hydro, the research that we've done so far has indicated that we're going to have to pay close attention the DC bus for charging and connecting with the inverter(s).

We're also not looking forward to the cost for the armoured cable to run between the sites — we're almost at the point where stepping up the AC voltage makes sense to reduce the cable costs.

Running the numbers through PVWatts for 6 kW worth of panels with Victoria, B.C. as a nearby location gives us a low of 174 kWh in December, and a high of 776 kWh in July. Assuming that during the winter months we'll have enough extra power from micro-hydro, in the summer when there is no water flow, we'll have around half of the power for the comms equipment, and 1.5 Kw to 3 Kw depending on the month in the summer for our home.

For the solar array, we're looking at constructing our own mounting system based around the T-Slots system, which we can secure to the rock bluff via drilled rock anchors. We'd site the inverter(s), generator and batteries in a small out-building nearby to the panels, and run feeder cables out from there.

Is anyone running an XW with the AC input from a micro-hydro or wind power source? Any gotchas with this configuration?

Any thoughts or words of wisdom from the forums for us at this point? We're currently doing our research to find out what options are out there, and what equipment is recommended.

Peace,

David & Laura

mike95490 · March 2011

Re: Gulf Island Off-Grid System

12KWh comm tower ? Ouch.

What's you penalty if it fails? Can you get diesel or propane for a PAIR of backup gensets ? If you can plan batteries for just 1 cloudy day and run genset, that's a lot better than a monstor battery for 3 days of clouds.

Lucky you havew hydro for winter. Plan on 2 of those also, a spare ready to install when the prime one siezes a bearing.

Photowhit · March 2011

Re: Gulf Island Off-Grid System

So is this "communication relay equipment" for personal use or an on going business, does it have to be "Up" all the time? so you need multiple redudent systems?

Ralph Day · March 2011

Re: Gulf Island Off-Grid System

Ah Mike...the voice of optimism. But listen up, he's speaking from experience.

icarus · March 2011

Re: Gulf Island Off-Grid System

Those of us that live fairly far off grid believe in redundancy. I have two (or more) of nearly everything important. Comes from the days of not being able to get spares easily.

Tony

techntrek · March 2011

Re: Gulf Island Off-Grid System

To overcome the distance issue you may want to look into a Sunny Boy with Sunny Island combination. This will allow you to have a high PV array voltage, thus smaller cables on your long run. Xantrex is also supposed to come out soon with a high-voltage charge controller which would let you do the same thing but stick with only one conventional inverter like the XW.

Is your comm equipment going to be a cell phone booster/relay? Just doing a cursory search I found one that uses about 5000 watts per day. The first step in building any system is conservation/reduction, so if you would be ok only running it 12 hours a day you would be down to 2500 watts.

The XW is a great system but you'll need to regulate the wind or hydro to standard 240 before feeding it to the XW.

BB. · March 2011

Re: Gulf Island Off-Grid System

techntrek wrote: »

The XW is a great system but you'll need to regulate the wind or hydro to standard 240 before feeding it to the XW.

To clarify, there are about four ways to feed power into an XW Hybrid Inverter (is fairly complex piece of gear--summaries are not going to it justice).

Through the 120/240 VAC utility grid input
Through the 240 (possibly 120) VAC generator input
Through the 24 or 48 VDC battery bank
Through AC Coupled / Backfeeding from a GT inverter backwards through the XW Inverter to the DC Battery Bank...

Normally, I would expect wind/hydro to feed in DC through the battery bank (with possible diversion controller required). Although you could figure out how to feed Grid Tied for local generated AC too...

At least, that is how I understand the XW System from 2,000 miles away.

-Bill

mike95490 · March 2011

Re: Gulf Island Off-Grid System

techntrek wrote: »

....
The XW is a great system but you'll need to regulate the wind or hydro to standard 240 before feeding it to the XW.

I think the common practice, is to use wild AC, rectified, lightly filtered and feed that to a MPPT controller that can accept the voltages from the turbine.

Midnight has about the best systems for wind power conversion

David and Laura · March 2011

Re: Gulf Island Off-Grid System

Re: Post #2

If we loose power, we have neighbours that will be unhappy with loosing broadband Internet, and if it was during business hours, we wouldn't be able to continue to work at our jobs.

So, yes, redundancy is important to us — The higher power load comes from dual uplinks and equipment to manage fail-overs.

We're planning to put in a 1 KV Liebert extended runtime UPS in the tower shed, and potentially have a second small generator located there in case we loose our main system.

As for the micro-hydro, we are looking at having a spare, since the lead time for getting a replacement can stretch to months.

Re: Post #3

It's not run as a business, but we use it for our business.

Re: Post #5

We're trying to design our system so that if components fail (and they will), we only have degraded service, rather than no service. That's why we've been considering if it would be better to have two XW4548s instead of a single XW6048.

Re: Post #6

We want to keep the inverter as close to the panels as possible to minimize the length of the DC run. Having the longer cable runs at 120 VAC or higher is far more efficient.

We'll get more accurate numbers for the radio and computer controller to see if we can reduce the load. Going with a low-power computer should help here.

Re: Post #7

We were leaning towards option #1 so we could still connect our generator through option #2. That way we could take advantage of the auto-start feature.

Re: Post #8

This approach would involve an an AC run from the turbine (and load diverter) to the building where our batteries are located, then a charge controller to the DC bus, correct? If so, wouldn't there be problems with having both the charge controller for the solar panels and the charge controller for the turbine connected to the same bus?

If both charge controllers were Xantrex and connected by XanBus, would they be able to co-exist?

Thanks for all the great feedback!

BB. · March 2011

Re: Gulf Island Off-Grid System

Midnite would output that power to a DC battery bank (at least the basic system)... Which would be where the XW Hybrid inverter would "manage the power" (Grid Tied, Local AC, AC Generator Support Mode, etc.).

-Bill

mike95490 · March 2011

Re: Gulf Island Off-Grid System

David & Laura wrote: »

Re: Post #5

We're trying to design our system so that if components fail (and they will), we only have degraded service, rather than no service. That's why we've been considering if it would be better to have two XW4548s instead of a single XW6048.

Compare the price difference between the 45 & 60. get a pair of 60's !

Photowhit · March 2011

Re: Gulf Island Off-Grid System

What kind of broad band do you need? (be sure to ask your neighbors to chip in)

If your doing a satalite based sysem, I would be sure to check and see if you can't get coverage via a WISP (wireless internet service provider) these are terestrial based system that use directional amplified antenna and souldn't come with such a high watt hour penalty. I was looking into starting one here in rural Missouri, but since I live next door to a nuke plant DSL is no problem. (only thing good about that plant) WISPs work up to 50 miles but more often 20-30. Well worth a little hunting and pecking on the web.

A couple links;

http://www.pcmag.com/article2/0,2817,2340369,00.asp

http://www.wispa.org/

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

http://www.trangobroadband.com/solutions/wireless-internet-service-provider-isp-wisp.aspx

David and Laura · March 2011

Re: Gulf Island Off-Grid System

Re: Post #10

We're going to stick with an AC output from the water turbine, but thanks for the pointer to the Midnight line of charge controllers. We hadn't come across them previously. Specs look good, though we're not too sure about their design aesthetics.

Re: Post #11

You're right — Given that the price difference is minimal, if we do end up going with two inverters, we'd go with a pair of XW6048s and not bother with the lower wattage version.

Re: Post #12

We checked with the local group that is providing wireless Internet, and the wattage from the radios that they use aren't that high. We're putting together a power budget, and seeing where it will come out to be.

The satellite Internet system is a pretty big power consumer.

We might be able to do a radio bounce to another island using the equipment that you pointed us to, but we'd have to figure out what to do on the other end. Perhaps this is something to explore as an alternative in a few years.

System2 · March 2011

Re: Gulf Island Off-Grid System

David & Laura,

To reduce your loads and increase production, consider:

1. Use as many DC loads as you can, such as lights, fans, telecom, computer, etc. Run loads at 24VDC if possible.

2. Don't use a UPS. It's an AC device that charges a battery. The power is converted four times (DC-AC-DC-AC-DC) by the time it gets to your telecom equipment. A waste of energy. You already have batteries. The system batteries can be your UPS.

3. In low-sun BC, consider using thin film modules which have higher efficiency at low irradiance and in diffuse light (cloudy weather). Good if panel space is not a big concern.

techntrek · March 2011

Re: Gulf Island Off-Grid System

David & Laura wrote: »

Re: Post #6

We want to keep the inverter as close to the panels as possible to minimize the length of the DC run. Having the longer cable runs at 120 VAC or higher is far more efficient.

I think you misunderstand the situation. You need as high a voltage as possible on your long run, DC or AC doesn't matter. Get your voltage up to let's say 350 volts DC from your PV, maybe you'll only need 8 gauge wire on the long run and then stick the inverter on the other end. The best voltage you'll get from an inverter is 240 and then you'll get voltage drop on the other end. Boost it on the DC side and then invert to AC close to your load to avoid the voltage drop.

mike95490 · March 2011

Re: Gulf Island Off-Grid System

techntrek wrote: »

I think you misunderstand the situation. You need as high a voltage as possible on your long run, DC or AC doesn't matter. Get your voltage up to let's say 350 volts DC from your PV, maybe you'll only need 8 gauge wire on the long run and then stick the inverter on the other end. The best voltage you'll get from an inverter is 240 and then you'll get voltage drop on the other end. Boost it on the DC side and then invert to AC close to your load to avoid the voltage drop.

Well, Grid tied inverters will take up to 500VDC, and the Xantrex High voltage charge controller (600VDC) is due out soon, but I think most other controllers, only have 150VDC inputs. This is an off grid system not grid tie, right ?

So, maybe waiting 5 or 6 months for the XW high voltage controller is the ticket, wire the PV in series, and moving 10 A DC from high voltage array to charge controller would be the ticket.

techntrek · March 2011

Re: Gulf Island Off-Grid System

Exactly. Boost the voltage the easiest (and least lossy) way to get to a high voltage - at the PV array - and then convert to AC close to the loads. I almost recommended another way which has been used in the past, mostly because it was the only way to get around the problem of long runs. Might as well mention it to cover all bases.

You could put the inverter near the array, and then buy two transformers to convert the 120 V or 240 V AC output to something higher such as 480 V AC, make the long run and then down-convert back to 240 V. This method has high losses in the transformers which is why it isn't the best method anymore, IMO. Best to do it on the DC side w/o transformers.

You want to stay away from the 600 volt limit if the XW can take it that high, partly due to code issues, partly because most wire has a 600 volt limit. I would keep it below 400 volts.

David and Laura · March 2011

Re: Gulf Island Off-Grid System

Re: Post #14

1. We're planning to go with LED lighting, so that will be a DC load, as will our fridge. Equipment with wall warts that put out 12V could be bypassed and run directly if we end up having 12 volt outlets.

What types of outlets are commonly used these days for DC? I've read about people using XLR4 connectors, and a geek friend of ours suggested that we look at using Cat5 RJ45 connectors and Power over Ethernet.

2. Regarding a UPS, we were planning on installing a Liebert unit we have to protect the equipment at the tower. We'll measure the efficiency of the unit and see how much power it's going to waste in the AC -> DC -> AC conversion, and depending on how the final configuration comes out, we may drop the UPS altogether.

3. Panel space is not a concern. We have a nice bluff that we're planning to use, and our current plan is to build a mounting assembly using T-Slots to attach to the rock face. (We're going to take a bunch of photos of it this weekend, and we can post them). So, we'll take a look at the differences in power levels vs. cost, and see if it makes sense. Given that we've got the water turbine during the months when we get the least sun and the most cloud, the thin-film panels may not be worth it if they are significantly more expensive per rated watt.

Re: Post #15

Ah, I think I understand now. With the high voltage charge controller, we can reduce our voltage drop, and with the length of the cable (less than 1000 metres), the vast majority of the losses will be resistive. Thus, by going to, say 400 volts DC, that would result in less loss than 120 volts AC.

Based on some preliminary pricing, it looks like it makes sense to use aluminium cable.

Right now, we're still determining the optimal placement for the tower. If the tower ends up being able to be sited on the same bluff where the solar panels will be mounted, over half of the loads will be right where the solar panels are. In that case, I think it makes sense to put the inverter there, and run AC to our homesite. If the tower is located in a different location, I think it would make sense to run a higher voltage DC to our homesite, have the inverter located there, and run AC to the tower.

We'll know a lot more once we finalize where everything will be physically located.

Re: Post #14

1. We're planning to go with LED lighting, so that will be a DC load, as will our fridge. Equipment with wall warts that put out 12V could be bypassed and run directly if we end up having 12 volt outlets.

What types of outlets are commonly used these days for DC? I've read about people using XLR4 connectors, and a geek friend of ours suggested that we look at using Cat5 RJ45 connectors and Power over Ethernet.

2. Regarding a UPS, we were planning on installing a Liebert unit we have to protect the equipment at the tower. We'll measure the efficiency of the unit and see how much power it's going to waste in the AC -> DC -> AC conversion, and depending on how the final configuration comes out, we may drop the UPS altogether.

3. Panel space is not a concern. We have a nice bluff that we're planning to use, and our current plan is to build a mounting assembly using T-Slots to attach to the rock face. (We're going to take a bunch of photos of it this weekend, and we can post them). So, we'll take a look at the differences in power levels vs. cost, and see if it makes sense. Given that we've got the water turbine during the months when we get the least sun and the most cloud, the thin-film panels may not be worth it if they are significantly more expensive per rated watt.

Re: Post #16

This is a off-grid installation.

Based on the preliminary specs, the new XW MPPT 80 600 looks like a nice piece of kit! Given that we won't be doing the install until the summer at the earliest, waiting isn't a problem for us.

Re: Post #17

We looked into using step-up and step-down transformers, and they sure do result in a fair amount of loss. It would almost be better to spend the money on larger diameter cable instead.

We'd keep it below 400 volts because the cable we've been looking at is rated for 600 volts, and our understanding is that when unloaded, a solar panel string can rise up to a higher voltage then when loaded.

Again, thanks for all the help! This is really helping us further refine the design for the system.

Photowhit · March 2011

Re: Gulf Island Off-Grid System

[QUOTE=David & Laura;808091. We're planning to go with LED lighting, so that will be a DC load, as will our fridge. Equipment with wall warts that put out 12V could be bypassed and run directly if we end up having 12 volt outlets.

What types of outlets are commonly used these days for DC? I've read about people using XLR4 connectors, and a geek friend of ours suggested that we look at using Cat5 RJ45 connectors and Power over Ethernet.[/QUOTE]

OK I know I have stated this before, without recalling where I had read it, so I tracked it down, and Backwoods Solar states;

"DC OUTLET & PLUG Handles 20 amps, fits standard outlet box & cover. Takes 10 or 12 gauge wire on the screw terminals. These are actually heavy duty 240 volt outlets which pass building codes for DC wiring if there is no 240 volt in the house."

This may well be old information, I had read this before, Wiles started rewriting the NEC code to include solar (I think, late '80's) At that time you could order catalogs from Real Goods, and Backwoods Solar and they had a wealth of information.

I think they both still put out catalogs that have good info, NAWS beats both for price normally! though the others carry odd things, like this outlet. Easy enough to search, I won't put up a link, the outlet and plugs can be had at most big hardware or an electrical supply store. Also might try checking out this information as it might no longer be true, just because they say so, don't nec.... or More likely it's legacy information and the code has changed since posted.

What your voltage drop on any 12 volt runs!

mike95490 · March 2011

Re: Gulf Island Off-Grid System

POE - is only for very low power items, the cables are thin, and can't handle even an amp at 12V, limiting you to items of 10 w or less. It was a signal system, and adding power to the data cable was a kludge, that works at low power levels.

niel · March 2011

Re: Gulf Island Off-Grid System

connection options for dc vary widely and could depend on the potential current drawn. most that have high current draws do not even have a connector, but may be a bolt with a nut and a washer or 2. it could even look like a standard bus used for ac grounds or neutrals.
for smaller currents actual connections may be employed like,
http://www.radioshack.com/product/index.jsp?productId=2062452
http://www.radioshack.com/product/index.jsp?productId=2103614
many items commercially made usually have either of those types of connections, but you can use other less common connections like banana plugs or rca type connectors. connectors can take out the risk of connecting something up backwards and it is recommended that fuses be used.

niel · April 2011

Re: Gulf Island Off-Grid System

i guess i should add that the bolts do not accommodate large wires very well so many will have a connector placed on the end of the wire like these,
http://www.solar-electric.com/teluwiha.html

dwh · April 2011

Re: Gulf Island Off-Grid System

Power over Ethernet is fine to power ethernet devices which support it.

Useless for pretty much anything else as it is a non-standard voltage.

The origiinal PoE spec was 15w @ 44v dc, the new spec is 25w @ 44v dc.

Photowhit · April 2011

Re: Gulf Island Off-Grid System

dwh wrote: »

Power over Ethernet is fine to power ethernet devices which support it.

Useless for pretty much anything else as it is a non-standard voltage.

The origiinal PoE spec was 15w @ 44v dc, the new spec is 25w @ 44v dc.

POE can be anything, I often use 2 different WiFi transcievers one takes 6V if the cable is oveup to 150' 7.5V for over 150' voltage drop brings the higher voltage back within tolerances and one that takes 12V but can handle up to 15V (as I recall) a later model with better regulation of the power.

TheBackRoads · April 2011

Re: Gulf Island Off-Grid System

dwh wrote: »

Power over Ethernet is fine to power ethernet devices which support it.

Useless for pretty much anything else as it is a non-standard voltage.

The origiinal PoE spec was 15w @ 44v dc, the new spec is 25w @ 44v dc.

X2 I would say PoE would not be a good method to power devices other than networking items..

David and Laura · April 2011

Re: Gulf Island Off-Grid System

Re: Post #19

It looks like going with a NEMA 6-15R is the best solution, and according to the updated 2010 PV and NEC: Suggested Practices document ( http://www.nmsu.edu/~tdi/Photovoltaics/Codes-Stds/PVnecSugPract.html ), it appears to still be code compliant.

A good visual reference of the different standardized plugs can be found at:

http://www.digitalissues.co.uk/html/docs/NEMA_Outlets.pdf

With respect to loss, assuming that we have our inverter and batteries in or near the house, we'll try to make sure that any DC loads (refrigerator/freezer, etc), are located nearby to minimize the run length, and we'll be sure to use larger gauge wire than the NEC minimums.

With respect to concerns about DC arcing, we may want to put a warning sign above the outlet to indicate that the device should be shut off or the disconnect breaker should be thrown before unplugging the device.

Re: Posts #20, 23, 24, 25

Thanks for all the feedback. It certainly sounds like something to stay away from. We were surprised given all these problems that it seems to be fairly widely adopted in enterprise networking, especially when we did some digging and found out that the wire used for Ethernet can't handle the full current specified by the PoE standard, nor are the voltages fully standardized, and this is despite the amperage being quite low.

Re: Post #22

This is a good idea. We'll look at crimping to a connector in this scenario.

David and Laura · April 2011

Re: Gulf Island Off-Grid System

We have photos of the bluff were we're considering installing our solar panels, and possibly locating the tower and inverter/batteries:

attachment.php?attachmentid=1685&stc=1&d=1302348532

Looking towards the south, photo taken at 11:40 A.M. in the morning.

Note the shadow showing that we've got a pretty high angle, even in early April.

The mountain to the right is the same one shown in the next photo:

attachment.php?attachmentid=1686&stc=1&d=1302348577

Looking towards the southwest.

The bluff is about 120 metres above sea level, and the mountain in the distance is 310 metres above sea level.

Under all that moss is pretty good basalt rock.

techntrek · April 2011

Re: Gulf Island Off-Grid System

I'd put the house up there, then put the PV on the roof.

niel · April 2011

Re: Gulf Island Off-Grid System

hey, that tree in the first pic looks creepy like it belongs in a horror flick.

8)

i'm wondering if some of the other trees may need cut or trimmed due to shading in the low winter solar angles. if you get very much snow then be sure to raise the pvs high enough so as to not allow a buildup at the base as the snow slides off of the pvs.

icarus · April 2011

Re: Gulf Island Off-Grid System

Looks like a Madrona tree, (Arbutis) Gulf Island almost never get any real snow.

T

XWGuy · April 2011

Re: Gulf Island Off-Grid System

If you are looking to hire a company to handle this installation, I would recommend Energy Alternatives, which is a company based in Victoria, BC. I don't work for them, but I have visited an installation that they handled on Gambier Island. They have the capability to handle the type of work you are planning. The site on Gambier had solar and micro hydro as well.

Gulf Island Off-Grid System

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