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Kevin Pegg

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since Apr 02, 2012
Smithers, BC Canada
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Recent posts by Kevin Pegg

Hi Darryl,

Firstly, the $12 controller is not an MPPT controller. False advertising. Read the reviews. Be best to buy several spares so that WHEN they fail you have new ones there on hand. At that price they are disposable-grade. Good controllers fail "open" so that they don't damage battereries. Check what the cheaop failure mode is - if it fails closed then the solar could cook the batteries real fast by over-voltage. And finally, does it allow the input voltage range that the solar panels produce? PV modules and controllers really need to be designed together. 250W panels these days are commonly in the 35-40 VoC (open circuit voltage).

Second, the battery isolator you suggest is not designed for this purpose. It is obsolete technology designed to charge 2 batteries from 1 alternator. They were common years back in boats / RV's etc with a dual house/start battery system. But always problematic. We now use electronic devices do do the same thing, without the losses. There is significant voltage drop associated with those isolators, so that means the inverter will be shutting down due to low voltage when the batteries are ok. And they fail constantly.

Your configuration _might_ "work" in the loosest sense of working, for a few months or so, with lots of fiddling. A good way to turn people off solar is having haywire systems that are unreliable and require constant fiddling and fixing. But you would find the batteries would get out of balance, needing to charge some and not others. And not to mention all the heavy cables needed to run that config. A 2 kW 12V inverter needs 4/0 wire. And that stuff is expensive.

A question I sometimes ask customers is "do you want power, or do you want a science project?"

http://www.blueskyenergyinc.com/
These folks make quality, low amp MPPT controllers. I have 100's out there in industrial projects.

http://www.midnitesolar.com/products.php?menuItem=products&productCat_ID=21&productCatName=Charge%20Controllers%20-%20Classics
This is the best MPPT controller on the market today. $800

http://www.midnitesolar.com/products.php?menuItem=products&productCat_ID=43&productCatName=Charge%20Controllers%20-%20KID
They have also just released a smaller version - 30A kid. $400. It will control 3 x 250W panels @ 12VDC, or 6 x 250W @ 24VDC.

Sticking to 12V means you will pay more for controller. Going to 24 or 48V reduces current (amps) and thus can get better value.

Hope this is useful.

Kevin
5 years ago
Cheaping out vs doing it properly rarely pans out. As the saying goes, you get what you pay for. Why spend money on good solar panels only to have them ineffective due to improper charge control? Or damage batteries by over or under charging?

Charge controllers are generally broken into two styles these days: PWM (Pulse Width Modulated) or MPPT (Multi Point Power Tracking).

PWM are older, more basic, lots cheaper, as they are simpler. MPPT will deliver about 25% more power from the same solar due to it's improved charge methods. Which you can google for full explanation.

The current capacity - Amps is where the money goes. An 80A controller will cost lots more than a 20A. And that's where higher DC voltage helps, as with a 48VDC system you can have 4x the amps than a 12V system. One common mistake is presuming 12VDC. It's a real pain to deal with.

Using a mess of cheap controllers and batteries and loss-inducing diodes will fail. And try pricing out the high current diodes needed to isolate batteries! Save yourself that hassle.

Kevin
5 years ago
Hi Folks,

I live on a 160 acre, established off-grid (solar and wind powered) homestead in the Bulkley Valley - Smithers, BC area. I designed and sold the solar/wind off-grid power system to the previous owners in 2002 and got to know them as friends. When they decided to sell the property it was a 2 second decision to buy and relocate up here from Vancouver Island.

This is my third winter up here, getting to know the land, building out the gardens and figuring out what is next. The land is great - lots of water (several ponds and springs), good sun exposure, decent soil just full of potential for small or large scale agriculture. The short northern growing season is new to me. Lots and lots of passionate farmers in the area willing to share knowledge. The whole area is very agricultural.

I built a shop / office building on the property in fall 2012 and have relocated my business to run off the land.

The last project completed in Fall of 2013 before freeze up was building up a Hugelkultur bed. Looking forward to growing lots on that this year.

A project for 2014 is a greenhouse. There is a very basic plastic one from the previous owners, and it extends the growing season significantly. Thinking a better designed, winter appropriate greenhouse will get into 4 season growing.

Open to the idea of other people joining in on the land somehow. 160 acres is a heck of a lot of land I am discovering!

Kevin

5 years ago
It's entirely possible to do what your asking here. Details, details, details however! I live off-grid, with solar and wind now and microhydro in the future, and it supports a full home, office, metal shop, wood shop, etc in Northern BC, Canada. I've got clients all over who also have similar setups.

It's best to get away from sizing based on 150 amp service, etc as that's all theoretical and look more towards kWh of energy is needed. There are two considerations - peak power - ie when all appliances running what's the peak power, that will help size the inverter and system. Then there is the daily kWh demand which is what your future microhydro or whatever needs to support. If it's a one person shop it's pretty easy as there are only so many tools you can run concurrently.

The main consideration for successful off-grid is no electric heating as a general rule. I have aux electric elements in my hot water system that I will dump surplus solar/wind energy into, but that's just me being a geek about using every but of energy I get in.

7 years ago
I have written a design guide focused on off-grid applications for solar (and other alternatives) that you can download free:

http://www.energyalternatives.ca/downloads.html

Kevin
7 years ago
A generic answer is "not even close" but the devil is in the details. It's very risky relying on marketing claims on very cheap low quality panels to keep your valuable food frozen.

I can help you with this, but the first consideration is where do you live, how are the solar panels mounted, and do they get unobstructed sunshine?

A word of advise, these cheap panel kits like this purchased from retail outlets are actually significantly more expensive than getting quality panels from your local solar geeks.

Basically, we need to determine, in kWh how much energy the freezer uses, then looking at the climate normals in your area, then can do the math and figure out how much solar input to meet that need.

Kevin
7 years ago
Hi Tal,

It can be baffling but this process can be smoothed out. But there are a lot of details. Here's how I go about designing systems:

- Create an energy budget and understand how many kWh per day of energy you need. This is a key process, a tedious task, but of critical importance. If you are generating your own power, you should know how much you need. This is all easier said than done. Firstly, no appliance label actually tells you how much power it _really_ uses; it focuses on the theoretical and is usually overstated by 30%. Ideally you take a power meter like the kill-a-watt and find out how much power something really uses. Bit of a pain, but good data means good system design. There's a template for this here: http://www.energyalternatives.ca/SystemDesign/default.html
- you will learn that phantom loads are absolutely deadly and unless you have lots of money and a big system are best avoided at all costs. That clock radio, persistently sucking energy can use more daily power than a microwave or kettle.
- then I figure out what nature offers you for energy. Solar, wind, microhydro and what it will take to generate that power, keeping in mind seasonal variations. That's a whole topic unto itself.
- it sounds like your plan is to use a generator to cycle charge batteries, so that you have 24hr power, and the generator runs as needed to charge batteries. There is a science to doing this efficiently. I've seen so many people wasting so much time and energy they'd be better off just running the generator 24x7 and use less fuel. There are losses and inefficiencies during the charge/discharge cycle so yes it's really possible to burn more fuel by cycle charging if not done right. To the subject line of Nickel Iron that's the wrong technology for cycle charging for sure. I've done a lot of these systems and currently building a 180 kW system to power an entire off-grid community.
- I can't speak directly to gasification; great if you can make it work, it's certainly doable and established knowledge. It is a significant effort for sure though unless you can somehow store the gas for later use. I'm not a fan of propane - very expensive fuel to burn, fussy engines and hard to find mechanics in some areas. Diesel is lowest cost fuel to burn / highest cost engine. Good for biodiesel options.
- common, true deep cycle motive power batteries like L16's or golf carts work well for cycle charging. I've got entire remote wilderness resorts running on L16's. Sizing of this will depend on your loads and how often you want to run the gen.
- You will want a good sized 24 or 48V inverter (12V is a real pain and best skipped) with a big robust battery charger integrated (called and inverter/charger - way better than two separate devices), so you can charge the batteries up as fast as possible by running the generator, and then the inverter will provide power when no generator.
- A system status meter tells you where your system is at capacity wise.
- as more renewables come online, your reliance on the generator is less and less.
- solar is very cheap these days and last forever. Fossil fuels are expensive and one time use. So it's a balance of how much fuel now vs solar later - but the sooner you can stop spending money on fossils and redirect to renewables the better.

Hope that helps.

Kevin



7 years ago
Nickel Iron batteries are expensive, they last forever, and they are terribly inefficient. IE the amount of energy that goes into charging them is many times the energy you get out of them. I've not had the opportunity to test them personally. But I've had many people trying to sell me these and dismiss concerns for efficiency as being relevant, and they lost me right there. It depends on priorities.

7 years ago
I have 3 MPPT controllers on my off-grid system. They will increase power output, I didn't datalog my old controllers enough to say how much, but I'd estimate in the range of 25% improvement. I had hoped to replace the 20 year old controller on my Bergey XL.1 wind turbine but my old unit is too low a voltage to benefit from MPPT.

MPPT controllers are becoming common as it's harder and harder to find low voltage solar panels - the bulk of the market is focused on larger grid-tie deployments with the solar panels common today in the 35-40 VDC range open circuit. Using a higher voltage solar panel on a lower voltage system just throws away power.

Older early-generation Outback MX60 controllers I've replaced with the Midnite Solar units, mainly because a) I've learned to really dislike Outback products from experience in this market, and b) the Midnite controller has several specific features that I wanted - higher input voltage (up to 300 VDC) as well the controllers are networked so I can look at their performance on my computer. They have an online component but not finished yet. This controller has a 5 year warranty and a unique "end of warranty tune-up" where you can send them the controller & $125 6 months before end of warranty and they will replace all wearable components and fully check it out, and then give an additional 2 year warranty.

http://www.midnitesolar.com/products.php?menuItem=products&productCat_ID=21&productCatName=Charge%20Controllers

Morningstar also makes a smaller and more restrictive unit for simpler applications. Top quality units haven't had a failed morningstar anything for many many years. Used in lots of industrial applications.
http://www.morningstarcorp.com/en/sunsavermppt
http://www.morningstarcorp.com/en/tristar%20mppt

MPPT controllers are WAY more sophisticated and complex and expensive than older Pulse Width Modulated (PWM) or very old on/off shunt style.

As for microhydro, yes the same Midnite classic controller above will work for microhydro (or wind). It will let you increase your transmission voltage dramatically, reducing wire size significantly. 12V is very restrictive and really only suited to very short wire runs ie 50'. With MPPT you could go as high as 300 VDC transmission and have the controller reduce the voltage to battery voltage right at the batteries. The 12V side of things becomes the restriction - so limited to 60A @ 12 VDC. Multiple controllers can be tied together to act as one unit if need more than 60A.

And in case anyone is curious, I don't work for any of these companies, but I am in this industry and have set up hundreds of remote people with off-grid power systems over the last 2 decades. I am very fussy for quality product as that $100 controller that fails may cost me $2,000 in travel to replace it. Just like any industry, there's a lot of junk out there these days. I recall that a decade ago with a bad batch of Trace C40 controllers, cost me a small fortune when there was a bad batch of them out there, all installed of course in the most remote locations possible. If your system is mission-critical, invest in spares!

Kevin

7 years ago