Archive for the ‘Alternative Energy Sources’ Category

When designing your power system that you will depend on for years to come, it is a good idea to start with your expected energy usage in your home. Typically this is called an Energy Budget. You can refer to my previous post Sizing a Renewable Home Power System to easily determine your Energy Budget.

You can also refer to the post on Basic Concepts of Electricity in order to have a better understanding of the designing process here described.

After you complete an energy budget you will have a better idea of the amount of power production that will be necessary to run your off grid home.

In our next post we shall describe how to select your system power voltage. Stay tuned.

Your solar battery bank is truly the heart of your renewable energy system. Batteries are used to store DC electricity during the daily charging cycle for use at a future time.

Since the time at which your peak charging occurs rarely coincides with peak production times (our experience) then batteries are used for energy storage.

Choosing your batteries is a critical decision in designing your renewable energy system. If your solar battery bank is too small, then your system will not perform well and your batteries will have a short life. If your battery bank is too large it will be difficult to maintain a full charge, again resulting in poor system performance.

Solar Battery Location

Your choice of battery location should comply with the Electrical Code, whether you install the batteries inside or outside.

The location should also be designed to keep the batteries warm (25º C is best), because their capacity decreases at temperature below 25º C. This means that if you choose to locate your batteries in a unheated space, you will need to insulate the area properly.

You will also need greater battery capacity to compensate for the losses at lower temperatures. Make sure your supplier knows about the planned location of your batteries.

The batteries and other equipment should be accessible for maintenance and inspection, but safety must also be considered.

Batteries may give off hydrogen gas during charging and can be a source of electric shock, so the room area where they are housed should be properly vented to the outside and kept locked.

In addition, other electrical components, which can also be a source of spark, should also be kept separately from the battery housing.

Do not locate batteries near sources of heat or possible sources of open flame or spark. Finally, read all of the manufacturer’s recommendations and warnings about the safe and proper use and handling of batteries.

Inside Locations

Batteries located inside the living space should be properly vented to the outside. For small cottage systems for example two 12-VDC (volt direct current) batteries, you need a vent that is at least 1 inch in diameter.

Keep batteries separate from the living space by housing them in special battery cases properly ventilated to the outside. For summer cottages keep batteries fully charged to prevent freezing in the off-season.

Outside Locations

Batteries located outside of the living space should be housed in a box or shed. In a very cold location, you can house the batteries in a buried container for a better temperature control.

In all cases, batteries should be well protected from the elements and be well vented to the outside. Battery maintenance varies with the type used.

Basic maintenance includes visually checking the electrolyte levels and regularly verifying the specific gravity with a hydrometer. Add distilled water as necessary, and clean and tighten the battery caps.

Also, check for any leaks or physical damage to batteries. Follow battery and charge regulator instructions.

In our next post we´ll start discussing how to design your own renewable –off the grid- energy system.

Until then…

Once your solar panels are up and running, the next obvious requirement is some sort of charge controller, since continuous overcharging will ruin the expensive battery bank.

Charge controllers intended for solar panels work by monitoring the battery voltage, and once it reaches full charge, the controller simply short the solar panel leads together. This doesn’t harm the solar panels but it does waste whatever power they are generating. The energy ends us up heating the transistors in the controller instead.

Charge controller

Simple Charge Controller Circuit

In a typical charge controller for a solar panel, the incoming battery voltage is divided in half by a pair of 3.3K resistors, so the trip points are adjusted to one-half the desired levels. Start at 14 volts for the trip points. The actual trip points will depend on your particular batteries, but a good starting point is 14.5 volts for full charge, and 11.8 volts for discharged. In this case, the trimpots should be adjusted to read 7.25 volts at TP-A and 5.9 volts at TP-B.

You will probably need to monitor your battery voltage through several charge cycles to determine the perfect trip points for your system.

Simple Wiring Diagram Showing the Charge Controller and Batteries.

Wiring diagram for charge controller and batteries

You can easily buy a charge controller on eBay or build your own custom made if you know how. Certainly the best option is buy an already built controller as this is a critical part of solar panel energy system.

In our next post we shall discuss the main points on building the battery bank. Until then…

This is our seventh post on the subject -Build Your Own Home Made Solar Panels-

In this post we shall discuss how to connect the solar cells together.

Let´s dive into it…

You will find little tabs on the back of the cells. Take your soldering iron and heat it up. Touch the tip to the tab and gently feed some solder onto the heated surface of the iron. Just one drop will do. Make sure you do all 4 or 6 of the tabs you find.

Wiring solar cells

The tabs on the back of the cells will form a line, one on top and one on bottom. The top tabs are negative and the bottom tabs are the positive leads.

With the drop of solder on the backs of the tabs gently place a copper wire lead onto the tab and heat it up. The wire will bond to the tab and connect the negative tabs together.

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Wiring solar cells

Use different color wire for negative and positive leads to avoid confusion.

The cells should be stuck down to the plywood base in the pattern you made before and the wires are gently fed through the back of the plywood.

Use enough caulking to secure the cell to the backing. We usually use some sort of silicone because is pliable and lasts long time.

Use each hole for two cells, one facing right and one facing left, so the lead wires will easily thread trough the holes. Be careful not to press too hard on the cells when you are attaching them. We usually use a small piece of wood to place on the cell to press evenly with, avoiding breakage

Do the same for the other tabs.

Solar cells backer

When you have all of the solar cells stuck down on the backing you will need to wire all of the same color wires together.

It is a good idea to make leads long enough to join the ends later. Test fit a couple of cells before you begin.
Remember to connect all of the positives leads together and the entire negative leads together, or your panel will not work properly.

This spaghetti of wires will get connected to a junction box outside of the panel. We put another piece of plywood on the back of this backer piece just to keep out the weather. Remember to coat it with three coats of epoxy too.

All of the same colored leads will be joined together and the positive and negative leads will be connected to just one wire leading to your batteries.

Use the glass to cover the front. You can use aluminum sealer strips that you can screw the glass down with or make your own from wood. Seal up all the edges and leave a drain hole in the bottom of the panel to let any accumulated moisture drain out.

In our next post we will describe How to Connect the Controller.

Make sure you return to this website and please share our post with more interested people.

First you will need a base to place the solar cells on in order to make a panel. You need enough solar cells (about 80) to layout a fairly large surface area. You will notice that there are two distinct sides to a solar cell.

The front looks kind of a blue color while the back looks very much like the back of a mirror. It is essential that you set up the cells with the blue or upper surface facing toward the sun.

putting solar cells together

Each solar cell will create not much more than one half a volt DC usually. The voltage remains the same. As the size of the cells increase, depending on what you get, the current or amperage will increase.

You can place the solar cells out on the floor before you begin, like a deck of cards. Leave a space between each cell of about one quarter inch. Arrange the cells in rows until you have a shape that is pleasing to you. You want to make the finished panels slightly narrower in the width so they are easier to handle, but you can do as you like.

Once you have the cells laid out in the pattern you want, measure the outside dimensions of the rows. You need to know how big to make the backing board. You will attach the solar panels to this board so you need to know how big it is.

backing board of solar cells

With 80 cells you should end up with a panel that produces approximately 100 watts of power.

You can use some plywood or any kind of strong lumber. The nice thing about the plywood is that you don’t have to join it together. After getting the outside measurements we assess what glass we will have to cover the upper portion of the panel. You can put 2 inch spacers on top with a ventilation space around the panels as well.

The glass will usually need a support in the middle too so leave room for that as well.

Let’s say that the layout of the cells added up to a size of 24 inches wide and 40 inches high including the spaces between the cells. If we wanted a 2 inch spacer in the middle and all the way around the outside to support the glass then our plywood should be cut to 30 inches by 46 inches. In this way we could fit the cells on the plywood and still have support for the glass.

Before you begin to put the cells down on the plywood we first treat the plywood with an epoxy sealer that is designed for UV protection. It sinks right into the wood and protects it long term from the weather.

The holes in the dividers will have the wires from the cells meeting and joining to form the circuitry of the panel. The holes also allow a certain amount of ventilation too. Make sure you put at least 3 coats of the epoxy on everything as it will be exposed to some rough weather at times.

Get any kind of soldering gun with at least 25 watt and use silver bearing solder for soldering purposes, which you will need in the next step.

In our next post connecting the cells together…