Oasis Montana designs and sells residential solar electric power systems

Oasis Montana Inc.
Renewable Energy Supply and Design
Call us!  406-777-4321
Fax: 406-777-4309
M-F  8:00am-5:00pm MDT
Contact us: info@oasismontana.com
Home Page: www.oasismontana.com

Alternate Energy System diagram layout

Here is a basic block diagram of how a renewable energy system works.

It is quite easy to start with a generator-inverter (gen/verter) system first and then add solar and/or wind once you get your feet on the ground and as time and money permit.


Index and Home Page

 Site Map

Figuring Power Requirements

Load Evaluation Form

Insolation Map

Sample Systems

A.E. Component Overview

Component Pricing

Efficient Refrigeration

Propane Refrigeration

Conserv AC Refrigerator/Freezer

Generators: Wind, Gas, & Hydro

Solar Water Pumping

DC Sub Pump Info

Xantrex GT Series Specs

Xantrex TR Series Specs

Xantrex  Sinewave Series

Solar Modules Specs

Air-X Wind Generator

Solar Fencers & Ant Charmer

RV Systems

Who We Are/How To Order

Used & surplus bulletin board

Subscribe to our mailing list

Contact us


Solar panels convert sunlight to DC electricity, which is stored via a charge regulator into batteries; DC loads can be run directly off these batteries.  Cables from the batteries go to an inverter, which changes the DC to AC to run the conventional household loads.  Occasional large loads (welder, table saw, 240VAC pumps, etc.) might necessitate the addition of a generator, which can also charge batteries (in low light conditions) while you're powering AC loads.  And, if you have a good site for wind (10-12 mph average wind speeds or greater), a wind generator can be easily added for additional battery charging.  Now, the technology exists  for you to  have solar  modules, or certain wind generators, with a special grid-interactive inverter--without batteries. And, as the months pass, these technologies will become more readily available.

Below is a variety of alternate energy components, and an overview is given of their function and how they interact in a system.

CONTROLLERS AND REGULATORS:  Even if you have  DC-only power requirements (as with a small cabin or RV system), you will still need a regulator for any module 10 watts or larger.  The nominal output voltage of most solar modules ranges from 16 to 20 volts--enough to "cook" a 12V battery system!  A regulator (or controller) is sized to accommodate the amperage of your incoming power from the solar array and its voltage output (12, 24 or 48V) and keep from OVERCHARGING your batteries.  You can also get a regulator that handles a greater amount of amps than currently required, if you wish to add more solar modules down the line.  Ideally, you will be using slightly less power than your array's daily output; your regulator will keep your batteries charged by dumping your array's input to the batteries until they are "fat", then keep them in that topped-off mode until your usage lowers the voltage.  The next day, when the sun shines, the process starts again.  Controllers come with quite an amperage range, and a variety of options.  E-mail us for your specific system requirements!

Controllers are also used to optimize voltage in water pumping systems, basically enabling the system to produce more water in lower light conditions by converting voltage to amperage.  In a wind generator, the regulator may be built into the unit or may be stationed at the battery bank depending on how the unit is configured. 

INVERTER and INVERTER SIZING:  Your inverter takes DC power from your charged battery bank and converts it to AC power for your typical household lights and appliances.  Once you've determined the number of watt-hours a day you require, your peak loads need to be ascertained  to properly size the inverter.  This is the amount of watts used based on all appliances and loads that will be running at one time.  A water pump and washing machine motor is an example of what may be the peak load requirements.  A 1/2 HP pump and washing machine will use about 1875 (adjusted) watts per hour.  If this represents your total peak loads, you'll need an inverter that will be able to supply at least 1875 watts of continuous power from your battery bank--say one in the 2000 watt range.  It's a good idea to start out your system with the size of inverter you plan to grow into, as upgrading to newer, larger models is costly. 

SOLAR MODULES:  We offer a wide variety of modules, with output warranties varying from 20 to 25 years for the larger panels.  Solar modules should be mounted facing due south with NO shading; if you plan to adjust the array seasonally, the winter angle will be latitude plus 15%, in summer, latitude minus 15%.  Since we typically expect the solar modules to last a minimum of 20 to as many as 40 years, do not skimp on a mount structure.  The panels are too expensive to let blow away!  Different sizes and makes of modules can generally be mixed in a 12V system.  However, in a 24V system, identical modules will have to be acquired in sets of two, and wired in series. Most battery-based home systems are 48V configuration, and most solar modules now have higher voltage. Our 24V modules can be series wired to easily achieve the 48V configuration, and the MPPT charge controllers will accept high input voltage and then step it down to whatever your battery bank needs.

The amount of power a solar module produces is equal to the intensity of the sunlight it receives; also, the output of the module is based on the load it's powering.  If you are charging batteries, the battery's internal resistance will affect the panel's voltage.  A module may be able to produce up to 20 volts, but the working voltage will be lower--around 12 to 15 volts.  This will reduce the real output of the module.   A 75 watt module working at 14 volts will produce a maximum of 61.6 watts (the module puts out 4.4 amps X 14V = 61.6 watts). 

While there are some modules that perform better in lower light conditions than others, shading will reduce the output of any solar panel.  By no means should any shade fall on the modules for two hours before or two hours after solar noon, and preferably not at all during the day.

BATTERIES:  The size of the battery bank will be determined by the daily watt-hour requirements and the desired days of storage capacity required.  Here's a formula for calculating your battery needs: Take your adjusted watt-hours per day x the number of days of storage required; take that figure x 2 (for 50% depth of battery discharge); then divide by the system voltage = amp hours (ah) of storage needed.  FOR EXAMPLE, let's say you need 2000 watt-hours per day and want 5 days of battery back-up; take 2000 x 5 = 10000; x 2 = 20000; divide by 24 (for a 24V system) = 833 amp hours of storage required.  If you're looking at 220ah capacity, 6V golf cart deep cycle batteries, we'd divide 833 by 220 to come up with four sets of 4 (as it takes one set of four 6V batteries to supply a 24V system).  So you'd need 16 of those 220ah 6V batteries to provide 5 days of back-up, at the discharge rate of 2000 watts per day, in a 24V system.

Ideally, we'd prefer that you not take your batteries below 30% depth of discharge, and NEVER below 50% depth of discharge.   Basically you need to put a little more power into your batteries than you use (about 120 watts for every 100 watts you take out). Batteries can be series wired to achieve the voltage desired (i.e. four 6V batteries for 24V, two for 12V, etc.).  We offer several sizes and types of batteries to best suit your system needs.

Most of the batteries we offer are the lead-acid type.  They do require proper maintenance to extend their life and work in an optimum fashion.  They prefer moderate temperatures -  around 70 degrees; for this reason they should be insulated in cold climates, and well-ventilated in warm climates.  They need to be "equalized" at least three or four times a year, and as often as monthly.   Equalizing refers to a "controlled overcharging" process whereby the voltage of the batteries is increased to where the accumulated sulfates are "cooked" off the plates and mixed back into the electrolyte solution.  During this process, the battery caps are removed and distilled water is added as necessary.   A hydrometer (tool for checking the specific gravity)  is used to check the electrolyte density of individual battery cells at this time.  The equalization voltage for a 12V system will usually be around 15 volts; for a 24V system, 30 volts.  Some manufacturers suggest their batteries be equalized monthly.  Go to this link, http://www.oasismontana.com/batteries.html, our new battery page, for more maintenance information.

We offer several types of 6V batteries  and 2V industrial cells.  Once we know the criteria for your back-up power requirements, we will specify the best batteries for your project, and, as we have distributor contacts all over the country, we can have many shipped to you with no freight charges (2V cells and Surrette batteries excepted).

GENERATORS:  A generator/PV hybrid system may suit your home; many clients feel the need to have a stand-by or back-up generator for prolonged low light conditions or for the occasional high energy demand.  Some people just have the generator, inverter and battery bank (called a gen-verter system), so when they're powering their big water pump (or some other large load) they can also be charging their battery bank to run smaller loads (lights, TV, etc.) after they've shut their generator down--to minimize the generator run time.  These folks do not plan to add solar to their system.  Generators use a gas internal combustion engine to convert fuel to AC electricity,  which can power large AC loads while batteries are being charged.  In fact, many utilize a generator with batteries and inverter in the construction phase, then add solar incrementally as can  be afforded.  During construction, large power tools can draw costly amounts of power--and would not be economical to run with photovoltaics.  But, while you're running a generator to power these loads, you can also be charging a battery bank.  When you shut down the generator, you can then, via an inverter, run smaller loads (lights, TV, microwave, etc.)  off the battery bank.  Solar can be added easily to these generator/inverter/battery systems in order to reduce or negate generator run time.  Let us know your power needs so we can specify the best generator for your system--or tell us what you have, and we'll design a system to accommodate your requirements.  It all comes down to how many watts per day you need.  For information and pricing on specific components, scroll down the price list and also click on the generator button.

WIND GENERATORS:  While being extremely site specific, wind generators may be a valuable addition to your battery charging scheme.  If you live where there is an average wind speed of 10-12 mph or greater, and you can mount your unit 30 ft. above anything else within 400 yards, you may have a terrific location!  In the right situation, wind generators can be more efficient and cost-effective than photovoltaics.  To find out the wind speeds for your area, contact your local airports or weather agencies for this information.  E-mail us your site information and power requirements, and we'll specify the best unit to meet your needs.  See additional information under wind generators.

WATER PUMPS:  Call us with your pumping project specifications.  We need to know the following:  your well casing size?  Well depth?  At what depth will your pump hang in the casing?  What is the output capacity of the well?  What times of year will this be used?  Is there a pump now in use at the site?  Will this be pumping to a tank or cistern, or is it part of a pressurized system?  How is the water quality (sandy, muddy, etc.)?  And, lastly, how many gallons per day (and in what seasons) are needed?  With this information we can propose a water pumping system for you.   Many pumping systems are battery-less, but we can add batteries for on-demand  usage.  We offer a variety of DC submersible and surface pumps, 117VAC pumps, and we can power your existing 230VAC model.  E-mail us your pump specifications and power requirements!  We have a basic water pumping system broken down by components--check out our water pumping systems on that page by clicking on the "Water Pumping" button.  For information on DC submersibles, click here.

ENERGY EFFICIENT APPLIANCES:  It is a fact that every dollar spent on energy efficiency will save you three to five dollars with your alternate energy system.  Your heating loads are NOT cost effectively powered by electricity; your electric stove, water heater, clothes dryer and furnace are much more efficiently powered by natural gas or propane.  Conventional refrigerators tend to be real energy hogs, so please consider an energy-efficient unit or even a propane refrigerator.  An energy-efficient refrigerator could (in many parts of the country) be powered by four 75W solar modules; a conventional refrigerator might take 8 to 12 MORE modules, with an appropriately larger battery bank!  Compact fluorescent lights have the look and feel of incandescent bulbs , yet use 75% less power.   When you become your own power company, any way you can reduce your electrical loads will save you money in the cost of your system.  We have info on efficient AC refrigeration as well as information on LP or Propane Refrigeration or  "Refrigeration" at this link: