Solar Power System

Submitted by fyl on 16 January, 2006 - 16:41.

This is the quick and dirty description of the solar power system I installed to make my office as grid-free as possible. It pretty much runs one computer system on 24/7 plus DSL modem and some other assorted equipment.

The system consists of:

The panels are mounted to 2" aluminum angle that I connected to the bolts that hold down the Nicalit roofing. Three #6 wires (one is a ground) run from the panels down to the controller. The controller regulates the voltage to make sure the batteries are not overcharged.

The battery bank is four Trojan 235AH 6V batteries connected in series-parallel. Thus, 12V at 470AH. This then is connected to a Trace marine inverter (I found the marine version reconditioned for a much lower price than a new regular one--no other motivation).

This would be all for a "normal" solar installation. The Trace inverters are designed to power stuff from batteries continually. But, they also have a 120VAC input which you would typically use to connect to a backup generator or, in the case of marine use, to shore power when it is available. My "backup" is to connect to the house power.

But, this would mean charging all the time when grid power is available. The alternative would be to manually monitor the battery voltage and connect the inverter to the grid when the voltage is low. But, I am just not a "do it manually" person.

Thus, the back controller (see http://www.nicaliving.com/node/3205 ). This is a circuit I built (using an NE555 integrated circuit for hardware geeks). It has two voltage level sensors and controls a contactor which connects the inverter "input" to house power. It is set so that if the battery voltage gets down to about 11V, it goes into charge mode and when it gets to 14.5V it stops charging. It is adjustable.

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Solar/DC power

Submitted by Alra on 21 July, 2008 - 19:52.

Eliminating DC/AC Inverters.

All that an inverter does is to convert pure DC current(from battery) into almost sinusoidal AC current.

Later the almost sinusoidal AC current is converted back into noisy DC current that its then used to run computers and their peripherals, gadgets, gizmos and most appliances.

A Concept... (easier said than done)

One of the main reasons for having AC current is the ability to transfer power from the generating location to a distant one, where the load(s) is/are located and since we have the solar panels and battery banks right in our premises, wouldn't it be better to run a short, heavy wire from the battery bank into a DC distribution panel inside our property?

The difficult part: Would be to tap from the distribution panel into every single gadget, bypassing the gadget's AC power supply and power it with the proper DC voltage.

Not a new idea, DC current was used in the XIX century to power incandescent lights and DC motors.

My $0.02 Cord.

Al

Can be done

Submitted by fyl on 21 July, 2008 - 20:01.

For some loads, this makes perfect sense. As an example, for computers you can buy a power supply that runs on 12VDC. One source is ITX Depot.

Many motors, electric drills being a good example, are "universal motors". This means they will run on AC or DC. If you have a 120V batter bank, all is well. If not, think about device use. If you are going to run it a lot of the time (an electric fan, for example) it is probably worth finding one that runs on whatever your battery voltage is. On the other hand, if you have a perfectly good electric drill that you use once a month, keep it and run it off an inverter.

There are 12V blenders, coffee makers and such. Unfortunately, the AC versions of these appliances tend to use a lot of power and the DC substitutes use a lot less. Thus, that five minute coffee brew cycle you are used to can become 20 minutes.

On the good news end, 12V lights are coming of age. I have been buying samples of various 12V LED lights to see what exists. Availability and brightness are going up and prices are dropping.

What I am saying is that many times a DC answer is right but not always. It depends on your needs, your battery voltage and such.

Loads

Submitted by Alra on 21 July, 2008 - 23:49.

For an industrial shop, such as a machine shop that is running lathes, milling machines, drill presses, etc. the DC power system, won't cut it, most likely it would need 3 phase AC current.

For the Geek Ranch, the DC system, could partially be a solution.

As I see it, most appliances here in the USA don't come equipped with an external DC adapter, so the trick would be, to open the appliance's chassis, follow the wiring pass the rectifier, measure or determine the voltage at the filter output Cap., then drill a hole in the appliance's case, and mount a jack for a DC plug. Do this for every single appliance...Not difficult but very tedious.

LED'S. It would be a nice project to assemble LED lamps in Nica, you can buy them bulk with their corresponding pull-up resistors(or you can determine the resistor's value and wattage). To achieve the proper brightness and voltage, LEDS could be wired in series, parallel or combination, They will run fine from battery voltage, any voltage.

Otherwise, LED's are very sensitive to HV spikes and line transients.

Al

Are they a viable solution

Submitted by nicareal on 22 July, 2008 - 10:03.

to light your home? What would be the candle power output?

I imagine this question is like asking "does it taste good?". The reason I am asking is that I am considering off the grid solutions that are practical and economical.

Thanks, Jon

Wait six months

Submitted by fyl on 22 July, 2008 - 10:29.

My advice is to wait six months. Over the last six months I have bought samples of a lot of different kinds of lights. Some are build from a zillion small LEDs (and I actually have a bag of 900 and built one such light myself). But, what is now available are one watt LEDs. Thus, things are changing.

I have bought some decent units using three to six one watt LEDs. But, prices are falling fast as production ramps up.

Being a geek and an early adopter, I have decided that a lot of the lighting in the Geek Ranch will be LED. What "a lot" means changes but, at this point, my guess is:

  • All the fixed lighting in the hotel rooms and walkways
  • The normal lighting in the restaurant and bar areas
  • All the fixed lighting in the geek cabinas
  • Most of the outdoor path lighting

That leaves table lamps, some bright outside lights as needed and high-level light if the restaurant or conference room were to be used for a meeting or presentation where you need light on a whiteboard or on the presenter. Also, kitchen lighting will not be LED (yet).

Today, the initial cost will be higher but the ROI looks good both in reduced energy usage and light replacement. As this lighting will be 12V, we will add batteries to the system and get automatic emergency lighting in case of a power outage.

What we are doing overall is fairly complicated but it basically boils down to:

  • Runs off the grid power things
  • Can run off the backup generator if the grid power goes off
  • Runs off batteries that can, if necessary, be charged by the generator

The design is such that short power outages (say 1 second to 20 minutes) usually don't require starting the generator. I say usually because you might have some event that required more power or it might be "make coffee for everyone" time but, in general, that which matters keeps working. On the other hand, an outage from 2 to 5AM would probably not require starting the generator even though it is a much longer than 20 minute outage.

Once it is in place I plan to document it in detail (including the mistakes we made along the way). I am actually waiting with tools ready to do the generator hookup and inverter. It should happen "last week" using Nicaraguan time. :-)

LEDS II

Submitted by Alra on 22 July, 2008 - 11:24.

Hola Fyl,

Would you share the experience on building the led lamp, or we have to wait until a formal report is produced?

I've experimented with LEDS rated at 3.6 vdc with a typical 20 mA current, I don't have the specs. at hand, but they are very bright, when these leds are driven by a PWM(pulse width modulating) dimmer switch, you can crank them up to a super bright 100 Ma.

Thanks,

Al

Sure

Submitted by fyl on 22 July, 2008 - 11:32.

I put three LEDs in series with a 220 ohm resistor. Then paralleled a bunch of sets of them.

The problem is that the light output will vary quite a bit with nominal battery voltages from say 12V to 14.4V you go from about 5ma to almost 20ma. But, LEDs are a current device so you can't just assume they will drop 3.6V.

The "right way" would be one of the following methods:

  • Regulate the input voltage. Then you could add a current limiting resistor that would be pretty close to right. For example, regulate to 11V and then add a 47 ohm resistor in series with three LEDS.
  • Put fewer LEDs in series (say 2 for 12V) so the voltage drop across the resistor would greater. Thus, the voltage difference would result in a smaller current change.
  • Longer string and higher DC voltage.
  • An active current limiter. There are special diodes that do this or a transistor or LM317 IC biased to current limit would do it. (See Wikipedia for approaches here. But, more parts and more cost. You could, however, design the current source to to handle multiple strings of 3 LEDs where each string would have a relatively small current limiting resistor to compensate for the differences between the various LEDs.

LEDS & OTHER STUFF

Submitted by Alra on 23 July, 2008 - 20:47.

Gracias Fyl for the quick reply.

The value of the current limiting or voltage drop resistor, could be found by simple Ohms law.

However if the voltage wont stay steady, the leds wont work correctly and they may even burn out.

Linear(adjustable)Voltage Regulator LM317, I'm using it in an application with aprox. 16 vdc at the input and 4.2 vdc at the output, it is driving 6 uv leds at @ aprox. 600 ma total current, it gets super hot, can't even be touched, (maybe i should get a bigger heat sink)lots of energy wasted across it.

Replacing the LM317, I tested a wide-input adjustable switching regulator TI PTN78020W and found that it works better, my guess is that it dissipates about 1/4 of the heat that the LM317 does, and it holds a steadier voltage.

Switching regulators are more efficient than Linear regulators, but they are expensive.

The LEDS i tested were Lumex # SLX-LX3054UWC, they are 3mm rated at 3300 mcd (millicandles), the 5 mm are rated up to 11,000 mcd.

Anyway, as you stated, the last word in led technology is not out yet(not your exact words).

Thanks

Al

Thanks

Submitted by nicareal on 22 July, 2008 - 10:49.

I am in no hurry on this. It will be nice to see how it works out for you.

If you take a 12 V deep cycle battery..

Submitted by Doug on 21 July, 2008 - 10:22.

down to 11 Volts you are cutting it's useful life about in half;

http://www.solar-electric.com/deep_cycle_batteries/deep_cycle_battery_fa...

http://www.lifelinebatteries.com/mcharging_procedures.php

"For maximum battery life in deep cycle applications, do not discharge the battery bank below 50%. "

States of Charge (SOC).

100% SOC 12.80 volts or greater

75% SOC 12.55 volts

50% SOC 12.20 volts

25% SOC 11.75 volts

0% SOC 10.50 volts

11 Volts is more than 75% discharge, A battery wise person advised me to get a cheap set of batteries for my first system cause "you're gonna screw 'em up, everybody does the first time"

I would be heart broken if I ruined a $1800 HUP or a multi thousand dollar bank so I started with a pair of marine (not true Deep Cycle) batteries , I haven't killed them yet but they have been severely tortured from my learning curve.

Each manufacture may have specific recommendations for their product depending on type; flooded lead, AGM, Gell

-Doug ©

If you're not part of the solution, you're part of the precipitate

Solar power suppliments grid power

Submitted by haircuttingcowboy on 23 August, 2006 - 10:29.

Fyl, if I understand correctly, your solar power system charges your batteries, which, with the inverter, allows you to use 120v AC current anytime (probably most useful whenever there is a power outage). And your solar power system actually feeds current into your panel box, if the batteries are fully charged. Thus, reducing your demand from the local utility company and reducing your electric bill.

How much was your electric bill before? And how much is it now, after the solar upgrade? Do you have a power outage daily? What sort of hot water system and cooking system do you have? Do you have an air conditioner (or need for one) or a heating system?

I was away, but I am back. I will have a look around n-l site to see what else is new.

Sorta almost

Submitted by fyl on 23 August, 2006 - 11:45.

The house, with the exception of my office, are on normal grid power. My office is always running on the inverter which, if needed, can also act as a battery charger. When it is in charger mode, the office is also running directly off the grid but it can switch back to battery quickly enough that computers don't go down.

Soon, most of the computers will run directly off 12V. Just more efficient and it means I am not depending on the inverter--one thing that can't get replaced locally.

It is hard to know for sure (until I get monitoring stuff in place) because of changes in who lives here and such but I guestimate I am saving $20/mo plus never having to deal with outages.

We may get 1-2 "quick" outages a week. I mean, 1 minute or less. A 10-20 minute outage happens maybe twice a month. Long-term (generally meaning 1-10 hours) happens every month or two. That's it.

Hot water is the typical electric shower heads. If the electricity goes off in town, the water quickly vanishes because the pumps aren't running so this is a non-issue even if you can't handle cold showers. Cooking is "like everyone else": bottled gas. And, well, no heating or air conditioning. Just not necessary. The closest I get is an electric fan sometimes.

a while back

Submitted by rich on 16 January, 2006 - 19:57.

we went into the issue of "NicaLit" http://www.nicaliving.com/node/880

Lots of cement but ...

Submitted by fyl on 17 January, 2006 - 07:57.

I don't know what is used for the fiber these days. In the US a neighbor used some ship lap siding on his house that seemed to be very similar feeling. In that, the fiber was sawdust but that doesn't see very useful for a roof.

The "old-style" Nicalit is not the shape of tile. It has one big hump and two little ones. That is the stuff with asbestos in it.

The decision for Nicalit was that I wanted something cooler than zinc but I didn't want the weight of tile. I'm happy with it.

Nicalit is Nicalit

Submitted by fyl on 17 January, 2006 - 08:27.

Yeah, you can just say Nicalit. I have the uncolored stuff. There is red and something else--probably green. The uncolored costs less. I am happy with the color and, as it is high above the street, you can't see it anyway.

Last year, a friend of mine asked me if I had ever drunk Toña as she saw it in a store in Seattle.

Tona is available in the

Submitted by 111 on 17 January, 2006 - 00:59.

Tona is available in South Florida and the Northwest US......those are the first places of the country they are distributing it in.....they started exporting to the US in 2004 I believe....

Tona(For Export): http://www.cervezatona.com/