Remote location in the Caribbean looking for the right balance

Re: Remote location in the Caribbean looking for the right balance

royalblood wrote: »

My daily watt hrs will be 2985 we can round that off to 3000 Watt hrs (
The house is basic
washer .
16 Cubic inch Fridge.
10lights 10watts each suckets ,No TV,
2 lap tops.
basic radio for news.

I could not find any solar radiation numbers for Trinidad (guessing that is where you are located)... Let us assume that you get 5 hours of sun for much of the year. You have 77% panel+controller efficiency, 80% for the battery, and 85% for the inverter. And you want 3,000 Watt*Hours of power per day.

• 0.77*0.80*0.85 = 0.52 efficiency from Solar panel to AC Inverter
• 3,000 WH * 1/0.52 eff * 1/5 hours of sun = 1,154 watts of solar panels minimum

If, you have significant cloud cover, your poor producing months can probably be down in the 3 hours of sun per day... So, you have a choice of using a generator (or AC Utility Power if available) and/or adding more solar panels:

• 3,000 WH * 1/0.52 eff * 1/3 hours of sun = 1,900 watts of solar panels during poor weather

I have access to 150 Ah 12 volts batteries. I am gathering that i would need 10 of these to give the power per day and also have charge for 2 other cloudy days.

For battery banks, we start with the rule of thumb of 3 days of no sun and 50% maximum discharge (for deep cycle batteries--automotive/truck batteries are not designed for this level of discharge and may fail much quicker).

• 3,000 WH * 1/0.85 inverter eff * 1/12 volt battery bank * 3 days * 1/0.50 discharge = 1,764 Amp*Hours

Now, that is a very large battery bank and your 10x 150 AH battery bank is very close to the recommendation. If you don't want that much storage--people have used 1/2 that amount--but they need to run their backup generator more often to keep the batteries from over discharging (taking a lead acid battery below 80% discharge / 20% state of charge, runs the risk of permanently damaging the battery bank).

The reason I made purchases on Inverter and panels is that i felt once bought i could add before the house is completed . I know i can add panels and or batteries.

Be careful with the inverter and power usage... Depending on what kind/model you have, the inverters can burn from 6 - 20+ watts just because the have DC power applied.

• 6 watts * 24 hours = 144 Watt*Hours just for a small inverter's idling current.

The Area is also windy am also looking at a 400 Watts Wind generator and 3 more 70 watt panels.

Location and tower height is very important for wind... Your site needs to be 300-500 feet from obstructions and the blades of the turbine need to be at least 30' above any obstructions. Typically, a tower would be around 60 feet tall as a minimum recommendation unless you have very clean prevailing winds. If they site has gusty/turbulent wind at the height you plan on flying the turbine--It is unlikely that you will get much useful power from the turbine.

Do you have any nearby neighbors that are running wind turbines? Are they happy with there installations? Have they run them for more than 1-2 years yet?

No batteries have been purchased yet ..I have the funds earmark for batteries and i have already sourced 10 x 150Ah Dry Matt glass 12V.

AGM (absorbed glass mat) batteries are about the perfect lead acid battery you can get (other than being roughly 2x the cost of flooded cell batteries). Very clean and efficient (use 90% efficiency instead of 80% that I used in the above equations if you wish). However, they are very susceptible to damage from over charging. Make sure you have good quality charge controllers (sun and wind) and it is recommended that you purchase Charge Controllers that have a Remote Battery Temperature Sensor Option to help better manage your bank's state of charge.

Also, since you cannot use a hydrometer to measure the specific gravity of your electrolyte (battery water)--I would highly recommend that you get a Battery Monitor (Amp*Hour / Watt*Hour meter that measures the current/power flowing into and out of your battery bank) of some sort to help you watch the state of charge of your battery bank.

Battery Monitors from our host
Victron Battery Monitors

Also, when wiring battery strings in parallel--you need to balance the wiring so that all batteries are equally charged and discharged. Here is a good site that describes several ways of wiring the battery bank in parallel:

Smart Gauge

Also, it is recommended that you place a fuse in each parallel connected battery connection to the positive bus... I know that many people do not do this and get away without proper fuses and/or circuit breakers. Always make sure your battery and wiring is in some place that a short circuit/fire does not place your family at risk (non-flammable floor, metal box, etc.).

-Bill

Re: Remote location in the Caribbean looking for the right balance

A good panel to battery ratio is in the area of 5%-13% (AGM can accept a wider range).

• 1,500 AH * 0.05 =75 amps
• 75 amps * 17.5 volt Vmp panel (assuming PWM controller) = 1,300 watts of panels

Now, if you are just storing the batteries (and have a generator to do charging when needed)--you could go down to ~1%:

• 1,500 AH * 17.5 Vmp * 0.01 = 263 watts to trickle charge bank

So, the choice is really yours--You need the panels (and backup genset) to replace the power you are planning on using, plus any losses.

The above numbers are just rules of thumb/estimates to get you in the right area.

Since you already have some of the components. Setup the system and monitor the battery bank state of charge (if you don't have a Battery Monitor, you will have to use an accurate volt meter (12.xx volt accuracy at least) to measure the resting voltage (and charging voltage) of your battery bank (and monitor charging current too).

Do you have any charging information or instruction manual for your battery bank? AGM's are nice batteries but you need to watch their voltage and current closely since you cannot monitor electrolyte specific gravity with sealed batteries.

Typically, for folks that have a generator and not many solar panels... You run the generator during the day to support large loads (saws, compressors, etc.) and charge your battery bank. And run from the bank+inverter for evening/night loads when you don't need much power and want to have some quiet time.

Also, you could run your small loads from the battery bank during the days when you are not using power saws and other heavy loads.

Ideally, you want to run your generator around 50% loading... As the loads drop, fuel flow typically remains around 50% and you start using a lot of fuel for a little bit of electricity.

-Bill

Re: Remote location in the Caribbean looking for the right balance

A small system may be 12 volt battery bank, 300 watt inverter, charge controller and 200-400 watts of panels. This would be large enough (for many people, of course, depends on your location, weather, and actual power needs) to run a few lights, a small pump to pressurize for sink/shower, a few lights, radio, and a laptop computer + some sort of remote Internet for a few hours per day.

A larger system would be 12-24 volts, 1,200-1,500 watt inverter, maybe 500-700 watts of panels (again, depending on area), a 2x larger battery bank, and you could add an energy star refrigerator or a chest freezer conversion (less power draw).

etc....

In the end, the most cost efficient solution is to start with your known power needs.

Of grid solar power is expensive. Costs can be reduced somewhat with used equipment and doing your own install.

In the end, most of the time, you need to do a couple different paper designs and see what is most cost effective for you and best meets your needs. Also, you need to look at your seasonal power needs... There is a point where it is, many times, cheaper to run a small gasoline/diesel generator to cover for stretches of bad weather/less than sunny times of the year.

You also mentioned being in a forest--Do you have an open area where you panels can get full sun (no shade) for much of the day?

-Bill