Designing a Solar Energy System for your house, RV or boat is not as complicated as some might think. You can figure out the type and size of the Solar Energy System that you’ll need by doing a few simple calculations. The first step is to determine whether you want a grid tied Solar Energy System or a completely off-grid Solar Energy System. In the case of a house, the first question would be whether grid power is available and if the answer is yes then you must decide which system you would prefer.
On a grid tied Solar Energy System (used mostly on land based applications such as houses or businesses), the solar panels will supply power on sunny days and on cloudy days or at night, the system switches to regular grid power from your local electric company. This is usually accomplished through an inverter (see picture below) or several inverters connected in parallel which act as the brain of the system switching to grid power whenever needed. These systems are typically used on homes or businesses where grid power is available in or near a town or city. Note: On a grid tied system, when you are producing more power than you need, the system will send all that extra power on to the grid and your local electric company typically buys it from you at the end of the month. To prevent accidental shock to repairmen, if the grid power fails (the system will automatically shut down when it senses that the grid power is down.) This can be a negative for some as in the event the grid power were to go down, you are essentially without power until it returns. (something to consider)
An off-grid energy system as the name implies is independent from the grid and it usually sends DC power from the solar panels or wind generator (see picture below) through a solar charge controller (see image below) which prevents battery over charge and maximizes the power sent by the solar panels, into your battery bank which stores it for later usage. You can then draw power from the battery bank through an inverter which turns DC power from the batteries into AC power for use on all AC powered appliances and electronics. You may also choose to connect the batteries to a DC panel for all your DC powered electronics. This Solar Energy System is completely self-reliant, although there is the option of having a generator or an engine alternator (in the case of a boat or RV) as a backup or in a house application, having the option of an AC power input from the grid into a battery charger or inverter charger (see image below) to charge the batteries on cloudy days or at night. This system is used on many off-grid applications including houses, oil rigs, RVs, and boats. Note: With an off-grid system you won’t have the ability to sell the power back to the electric company, but you wouldn’t lose power if the grid power were to fail.
There are a few key components to consider with both types of Solar Energy Systems. On a grid tied Solar Energy System you can calculate the size of your inverter and solar panels by simply adding the startup wattage of all your AC powered electronics or (if available) by simply looking at your electric bill which will give you the number of kilowatts you consume in a month (you can then multiply times 1000 to get the number of watts and divide by 30 to determine number of watts consumed per average day). With this information you can determine the number of solar panels you’ll need and number and size of inverters. (Go bigger than needed on inverter size since there is always a power loss when going from DC to AC)
On an off-grid Solar Energy System you must also calculate the size of the battery bank by calculating your Amp Hours needed over a 24-hour period by dividing the wattage needed by the voltage of the system you are going to install (12V for smaller systems or 24V ,36Vor 48V for larger systems) will give you the AH (Amp Hours you will draw from the batteries in one day to determine the size of your battery bank. Note: Your battery bank must be able to store enough power to supplement the system at night and on cloudy days as there is no grid power to fall back on and to minimize the use of a noisy generator as much as possible. Also keep in mind that depending on which battery type you choose, you must oversize the battery bank to extend the life of the batteries.
What type of batteries do I need and what size?
The most popular choices are Lead Acid, AGM, or Lithium. Lead acid batteries, although cheaper to buy (initially) are more expensive per charge cycle than the rest, have less life span and their life span is dramatically reduced through a process called sulfation when they are discharged less than 70% total capacity regularly so typically you must buy a much bigger and heavier lead acid battery bank than it would be the case with AGM batteries or Lithium batteries (rule of thumb on a lead acid battery bank is to get at least 3 times bigger battery bank in terms of amp hours (AH) than what you would consume in one day thus preventing the battery bank from getting below a 70% charge even if there was no charge added during the whole day). example: if you consume 200 AH in a day you may consider going to 600-800 AH on the battery bank to maximize battery life by reducing sulfation.
AGM batteries charge more quickly than conventional lead acid batteries, have low 3% monthly self-discharge rates and are maintenance-free—no need to add water. The spill-proof, valve-regulated design eliminates acid spills and terminal corrosion. AGM batteries are safer to operate than conventional lead acid or flooded batteries, as the chance of explosion or acid spray is reduced which allow them to be installed in almost any location and any position (except upside-down). Rule of thumb on AGM batteries is to go at least twice as many amp hours on the battery bank size than what you would consume in a day, so the batteries don’t go below 50% charge and the battery life is maximized.
- Lithium batteries meet all your power needs with less than 1/4 the weight and space.
- Lithium battery has 6 to 8 times longer life than lead acid.
- ½ hour to 2-hour recharge times (FOUR TIMES FASTER THAN LEAD ACID).
- Saves engine or generator running time and fuel.
- 3 Times more energy harvested (Replaces: 6.4V, 9.6V, 12.8V, 16V, 24V, 36V, 48V, etc.)
- Continues to perform the same and accept fast charging even towards the end of its life, unlike lead acid batteries in which the performance decreases dramatically in the last 1/3 of battery life.
- Continues a consistent voltage output even while battery charge is low unlike lead acid batteries.
- Higher reliability and less replacement associated costs and delays.
Because of the unique chemical composition of lithium and the fact that lithium batteries can go to a very low charge without damage to the batteries or a significant reduction of lifetime charge cycles, the rule of thumb is to go at least 20% bigger in terms of Amp Hours needed in one day.
AGM batteries are a great option if Lithium is not in the budget, however Lithium continues to be cheaper per charge cycle because of a longer life span and the fact that they are able to be discharged as much as 90% without damage to the battery thus allowing for a smaller and lighter battery bank which can be a consideration especially when space is limited.
Once you’ve figured out the type of Solar Energy System you’ll need, the number of the solar panels, size of inverter and size of the battery bank the hard part is over, now you are ready to design your system and either have an electrician install it or if you are a do it yourselfer you can do most or all the installation yourself (depending on the application).
There is a huge worldwide effort to be less reliant on fuels that cost us money continually, making a few companies rich but harming our air, water, and land in the process. No matter what your power needs are, you’ll find that adding a solar energy system, although it represents a good size investment at first, it can be quite rewarding both in terms of long term savings and freedom from electric and fuel bills. For more information on the products discussed here, simply click on the product images or visit us at www.SeaPeopleDepot.com