Solar Electric Question & Answers

This basic question and answer page is designed to help anyone understand the sequences of events for purchasing and contracting to install a solar electric system. If you consult with a licensed solar electric contractor, this will help guide you in your decision making process.

A) WHAT IS THE NORMAL SEQUENCE OF EVENTS WHEN PURCHASING AND INSTALLING MEDIUM AND LARGE SOLAR ELECTRIC EQUIPMENT OR MAKING SOLAR ELECTRICAL CONTRACTING?

1) Go to the "About Solar Energy" on our home page and read the details. Carefully read the articles related to "sizing your load", because you will begin by sizing your load. Review the Solarandu Solar Products Catalogs or similar product catalogs; 2) Make an appointment for an initial consultation with a licensed solar contractor who will eventually plane an "on-site inspection".

B) BEFORE MAKING A PURCHASE, WHAT ARE MY MAJOR CONSIDERATIONS AND HOW DO I KNOW IF I HAVE A GOOD SOLAR SITE?

1) A solar site analysis can be used to determine a roof or ground location that is not shaded from 9am to 3pm in the winter and 9am to 4pm in the summer. Most licensed solar contractors have a solar site shading analysis tool for finding the best location; 2) Decide whether or not you want to purchase equipment and plan to install the system yourself or if you want a licensed local solar contractor or a licensed electrical contractor and roofer to install the system. There are differences in cost based on the services provided; 3) Purchase your system based on your budget, your present needs, and future expansion potential for more solar electric power and/or batteries. At this stage a licensed solar contractor can benefit you the most on matching the proper components (wiring size, charge controller, etc.) for future expansion.

C) IS IT RECOMMENDED TO GET A LICENSED ELECTRICIAN INVOLVED?

Usually, county or city permits are required for most solar applications. A CVC state licensed solar contractor can contract to install the solar electric (PV) modules, the batteries, and the inverter (the balance of systems). A CVC state licensed solar contractor is also uniquely licensed and insured to make penetrations in a roof in order to attach solar collectors to the home. The solar contractor is not, however, licensed to make electrical hookups to the AC circuit breaker box. A licensed electrician must make all the following AC connections:

1. Connecting AC power from the inverter to provide power to the circuit you choose to solar power in your home. For Example:

A. You need to have an electrician hook up a sub-panel circuit breaker box and transfer switch near the main circuit breaker box to put in those circuits you wish to be solar powered daily.

B. You may have the electrical contractor install a transfer switch that will drive power to the other circuit breakers during an emergency (i.e. utility power outages or hurricane)

2. To back up the battery bank during periods of low sun conditions, you may need to provide AC utility grid power to the inverter's battery charger. You can use the utility company to back up your system and "maintain the batteries" during cloudy weather cases; a great way to take advantage of utility power. If allowed by the grid authority administration rules, you may also need a licensed electrician to provide a connection from the inverter to the AC circuits in the home, and sell back your eventual surplus energy to the grid company.

D) WHAT ARE THE MAIN COMPONENTS OF A SOLAR ELECTRIC SYSTEM?

Regardless of the nature and the size of Solar Electric Systems, all Solar Systems have Solar Modules where electricity is generated from sunlight. A DC/DC Controller regulates power to and from batteries in order to prevent rapid or excess recharging or discharging of the batteries bank, thus insuring a long life for the batteries. An inverter changes low voltage DC current to high AC voltage which is supply to power AC appliances. Inverters' battery charger converts AC electricity (from generator or utility power) to DC power which serves to recharge the bank of batteries. Fusing-Breakers and Disconnects are the over-current protection. Fixed mounts or Tracking Mounts support and guide modules toward the sun. The combiner box encloses the batteries for paralleling module output, and stores DC current. The batteries bank and its accessories are usually omitted in an on grid connected system; nevertheless there are necessary in high security or emergency installations (i.e. hospitals, data conservation centers...). Meters and monitors report system status and power flows, both instantaneously and cumulatively. The Power Center combines controllers, monitors, overcurrents, disconnects, and lightning protection; all together in one enclosure.

E) WHAT ABOUT RUNNING DC LIGHTS, FANS, LIGHTS OR OTHER APPLIANCES?

DC systems are usually small, using only 300 watts or less of solar panels. Usually, AC wiring in conventional homes and AC wall switches are not appropriate for DC power. DC systems are generally use for lighting up outdoor signs, billboards, etc and for water pumping systems for cattle. Often, homeowners will power ceilings or porch fans directly by DC power. Some remote homes have small DC lightings. However, most conventional homes use an inverter to change DC power to conventional AC much like the utility company's AC current for normal, everyday appliances in the home.

F) WHAT ABOUT INVERTERS ?

A good designed inverter will come with a built in battery charger and makes a pure sine wave equal to utility grid power; thus, will be acceptable for most appliances in your home. It is suggested that you review the Solarandu list of inverters or talk to a CVC solar contractor to see what inverter will meet your particular needs. The inverter should be sized for all the loads or circuits that it will power to all be on at the same time, plus the ability to handle starting surge currents, mostly from well pumps or other motors.

G) WHAT ABOUT WATER SUPPLY OR WELL PUMPING CONCEPTS IN A SOLAR HOUSE?

There are typically two types of solar wells or water pumping systems. DC Solar Direct and AC pumps that use inverters and batteries. Not only are DC Solar Direct systems cost less, there are now more reliable than wind mills or hand pitcher pumps. This is a natural for providing unpressurized water for cattle or other livestock. The hookup is simply two wires attached directly from the solar panels to the pump. Whenever the sun shines, it pumps water into a water trough. THE MAIN QUESTION IS WHETHER OR NOT, YOU NEED PRESSURIZED WATER FOR YOUR HOME. You typically need a cistern or water tower to produce pressurized water with DC pumps. Some DC well pumps can produce pressurized water with a large battery bank. However, it is usually much more cost effective to use a conventional AC well pump, commonly available and easily serviced from well drillers, powered by the properly chosen sine-wave inverter to produce pressurized water for the home.

H) HOW SHOULD I PLAN MY HOUSE FOR SOLAR POWER AND WHAT IS PRACTICABLE TO POWER WITH SOLAR ENERGY?

1) Make sure you have a solar hot water heater to pre-feed a backup LP gas or electric water heater. Try to avoid using electric water heaters only. 2) By spending $1.00 on energy efficient fluorescent lights, appliances, etc you will save $4.00 on the cost of solar electric equipment (solar panels, batteries, inverter etc) to power energy inefficient loads. For example, a 25 watt fluorescent bulb will give the same amount of light as a 100 watt incandescent lamp that uses 4 times the solar power. All of the products listed at the Products&Services section in this website are energy efficient appliances (unless otherwise specified). You can also go directly to the section energy efficient appliances for all kind of energy efficient products (including non-solar products), or send $4.00 to American Council for an Energy Efficient Economy (1001 Connecticut Ave NW suite 801; Washington DC 20036-5504) to get the current list of energy efficient appliance ratings on all types of appliances. (See SIZING YOUR SOLAR POWER SYSTEM). 3) In remote homes, use as much LP gas for refrigerators, stoves, water heater back-up, home heating, clothes dryers etc as possible. A super efficient modern refrigerator (preferably non-frost free) is also recommended. Do not plan to run ordinary air conditioning with solar power in remote homes unless you have a heavy duty generator backup, a large battery bank and a strong enough inverter. 4) In a grid connected home, start by putting some of the AC circuits on with an inverter with a battery charged power backup from grid power during bad weather conditions.

I) DOES IT MAKE A DIFFERENCE BY DESIGNING A SYSTEM FOR 12 , 24 OR 48 VOLT DC INPUT?

Yes. Usually, only small DC lighting systems and a few specially designed appliances are 12 volt. Most household systems will use a DC to AC inverter with solar panels and batteries arranged at 24 or 48 volts to be converted to 120V and/or 240 volt AC electricity. In most cases, money will be saved on 48 volt systems due to a simple fact that all the DC wiring, for solar panels, batteries, etc must be larger and therefore more expensive for 24 volt systems. We suggest 48 volts system for grid connected systems.

J) WHAT KIND OF BATTERIES ARE BEST?

Car batteries or marine batteries are not recommended; use the heavy duty deep cycle Trojan 6 volt batteries, or the heavy duty deep cycle 2 volt commercial batteries, or similar batteries. Typically, 6 volt 220 amp hour golf cart or 395 amp hr deep cycle L-16 's are put together in series for 12, 24, or 48 volt strings and in parallel strings to increase amperage. Water Miser safety vents are recommended on these batteries as water recyclers. Batteries must be in a secure locked location and well vented. Battery Monitors are recommended

K) WHAT ABOUT USING GRID CONNECTED POWER OR A GENERATOR TO BACKUP THE BATTERIES DURING BAD WEATHER OR FOR HEAVY LOADS?

The most popular remote or utility backup home power systems are hybrid systems, where a gas or diesel generator or utility power or even both are operated only occasionally to run high power consumption tools, etc. and/or to provide backup power during bad weather and/or to maintain and increase the life of the battery bank.

The most efficient inverters have-high powered programmable battery chargers built right in. This makes running a generator extremely cost effective since the power that the load doesn't use is not wasted, but is being stored in the battery bank. The inverter powers the load and acts as an energy recovery device for the generator or uses utility power as a battery maintainer. Most importantly the "photo-gen" or hybrid system can reduce the cost of a solar electric system by as much as three quarters. Only a minimum of run time is needed each week to provide abundant A.C. and D.C. electricity. Solar electric power can be added as the budget permits, until the generator or utility grid power is relegated to minor backup status or eliminated.

The first step is to size your solar power station by determining your daily power needs or your load. If you cannot do it alone, go to Solarandu World-Wide-Network  and call the nearest office for assistance. If there is not a representation in your region, ask for help from a qualified technician. Once you have known your daily load requirements, then you can determine the size of your battery bank, the proper inverter, and the size of the solar array. Until you arrive at your needs by calculating your daily electrical load, you cannot make an intelligent purchase decision or plan for future expansion on your system.

Once you have calculated your load, the next stage is to determine your autonomy based on year round weather conditions at your site. The most cost effective method is to base your requirements on the AVERAGE DAY of the year, while using a generator or utility power for infrequent large loads during bad weather. More storage means a greater capacity and deep-cycle battery bank; a larger daily load means a greater photovoltaic array. There are three paths to energy independence: conserving to reduce power consumption , purchasing a solar array capable of providing power storage during extended bad weather (we do systems on this scale), or augmenting with a small generator or utility power. The combination backup method can extend, even triple, the life of your battery bank by preventing it from being cycled too deep and too often. Choosing a generator should be based on your local requirements: mainly the chosen inverter, the pump and motor surges. If utility power is available to back up the battery bank, its probably best to get a inexpensive gas AC generator for emergencies weathers from tsunami, hurricanes, tornados, etc.

If you live in a remote home and need backup during bad weather or for short periods of heavy daily loads, we recommend a high quality DC Direct permanent ceramic magnet diesel generator -like Fischer Panda - or a high quality industrial type diesel AC generator that can be locally serviced and is designed for heavy use. Some options to look for are continuous duty rating and full wattage output on each generator circuit, voltage regulation to match your load, and surge power delivery for starting induction motors such as well pumps.

L) CAN ONE SELLS POWER BACK TO THE UTILITY COMPANY?

Technically, you can safely sell electricity from the sun directly back to your utility.

Connecting your PV system to the utility grid will require you to enter into an interconnection agreement and a purchase and sale agreement. In most countries, state's public utility commission regulations require utilities to supply you with an interconnection agreement. A few utilities have developed simplified, standardized interconnection agreements for small-scale PV systems.

The interconnection agreement specifies the terms and conditions under which your system will be connected to the utility grid. Some systems have been developed to meet all interconnection requirements and have the batteries and non-batteries options.

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