Assembling a system over time

hemmjo

I found this forum while searching for advice and components for an off grid system.

The situation;
I work with a mission group in the Dominican Republic. We have purchased a small piece of land which are developing as our base of operations. The power grid is 1/2 to 1 mile from the property over rough terrain. Even if we had the grid within reach, it is unreliable, on only 4-6 hours per day, sometimes off for days at a time. When it is on, it is always under voltage which requires step up transformers to boost voltage for each device(or one large EXPENSIVE transformer). I have not yet even investigated the cost of getting power to our site. I cannot imagine it would cost any less than building our own power system. We get 10 hours of daylight in January, 15 hours in June.

So, we need an off grid power system. Our power needs are not huge, we need to water pump and want to have refrigeration. Lighting is not a big issue, our participants bring LED flashlight and batteries to last them for their stay, AND it is VERY COOL to watch the sky with no lights on!!!!

As with all small mission projects, money is a huge issue and we must use what little we have wisely and SLOWLY. We already own a Honda eu2000 generator we can use to run things initially. However I am trying to develop a plan to develop our power system slowly over time, as funds allow. I want to be sure we do not waste money by purchasing things now that will not be able to be integrated into the system as it grows.

I have calculated our tentative needs, they are no more than 4KWH per day. With this in mind, I am thinking the system should grow in the following manner.

Step 1. Use generator to run refrigeration and water pump. Turn on and off as required to keep things cold and water storage tank filled tank filled.

Step 2. Add batteries and inverter to run appliances and water pump, and use generator only to charge batteries.

Step 3. Add charge controller and solar panels as money becomes available to charge batteries. The generator would them only be used during rare days the sun does sun all day.

This plan may take 1,2,3 or more years to complete, depending on finances and things we learn as the property development moves along.

My initial questions are in regard to choosing a charge controller for now and future. Since we already own the things we need for step one, the next step is to use the generator to charge the batteries. I understand the need for a good MPPT controller when we get to the point we can install solar panels. What I am not clear about is how the generator will eventually interact with the charge controller, solar panels, and batteries. Is there a charge controller that can interface the generator, future panels and the batteries? Or do we just need a good deep cycle battery charger at this time, then add the charge controller when it is time for the panels to be installed.

Thank You,

John

westbranch

Re: Assembling a system over time

Welcome to the forum. Before we can give advice we need to know more accurately the loads you will have, also is the Mains 110 or 220V?
your idea has some merit but there are some issues with building up as system in pieces. You first need to plan the whole system and then look to see if you can segment it.
step 2 &3 may be the tricky part but that can come later once you make some basic design decisions.

hth

Cariboocoot

Re: Assembling a system over time

Welcome to the forum John.

Okay, I think I've lost track of how many systems like yours I've helped design.

You've got a good plan going, although you may find that pumping water and running refrigeration are actually two of the biggest power consumers.

There are two ways to integrate your generator to the batteries & inverter. The first and easiest is to buy an inverter with a built-in charger. The second is to buy a separate, stand-alone battery charger. The generator does not connect to the charge controller. They will work together, as each charge source will look at the battery Voltage independently and adjust its output accordingly. There are certain circumstances where the two can dump a lot of current to the batteries, but this usually does not happen.

How are we doing so far?

hemmjo

Re: Assembling a system over time

Thanks to both of you for your responses. I do realize that refrigeration and pumping water are power hungry applications but they are also the most essential.

In response to the questions, all loads will be 110-120.

My preliminary figures come out to about 4KWH per day. BUT, this is just from using the yellow "energy usage" tags on refrigerators and freezers not real data. We will collect data during this season before we make any firm plans do.

I am thinking a stand alone charger will be the way to go when we get to the point of installing batteries and inverter. This will be some time down the road as funds are limited. We do have the generator to get us through this season.

Thanks,

John

stephendv

Re: Assembling a system over time

hemmjo wrote: »

I am thinking a stand alone charger will be the way to go when we get to the point of installing batteries and inverter. This will be some time down the road as funds are limited. We do have the generator to get us through this season.

Good plan, certainly doable. Regarding separate charger, I'd suggest you get an integrated inverter/charger since it doesn't make any sense charging batteries if you can't use them to power loads, i.e. you'd be buying inverter and charger at the same time anyway. Integrated inverter/chargers are cheaper than two separate units and they allow for automatic transfer when the generator is running.

BB.

Re: Assembling a system over time

I am a big believer in balancing loads with battery bank with charging resources... For example, you probably don't want a 6 kW genset if you only need to supply 1,500 watts of loads. You could end up spending a fortune in fuel to keep the genset running (larger gensets may consume 0.5 to 1.0 gallons per hour or more; smaller gensets may burn around 0.1 to 0.25 gallons per hour--much easier on the wallet if you can keep your loads small). And diesel engines tend to want ~40-60% minimum load to keep them burning clean (avoid "wet stacking" and glazing the cylinder walls).

Gensets tend to become less fuel efficient when operated under ~50% of rated load (gasoline engines tend to consume about 50% of rated fuel flow at 0-50% load--Inverter/Generators like some Honda/Yamaha/others can do a bit better at low loads because they can throttle the engine RPM down with light loads).

-Bill