Solar: Basic Science

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When it comes to “personal” solar usage many people fail to realize the simpler the better. We have fallen into the “more complicated the better” mindset which, in my opinion, originates with the cell phone. There was a time being able to make and receive a phone call without being attached to a land line, was not only amazing, but quite efficient and solved the number one issue of being able to communicate from any location.

However, today if the cell phone, I-pad, smart phone, whatever, doesn’t take professional grade photos, emit music as if you were in a symphony hall or order you pizza by you simply thinking about it, its of little value and is about to be replaced by a newer version. Lost is the original intent of making and receiving a phone call.

With this mindset it’s sometimes difficult to remain on task when discussing solar energy, which is …. to harness the power of the sun to produce energy that we can convert to our use. That form is usually electric, but could also be heat-transfer for specific use, such as hot water heating systems.

Quick History Lesson: Solar photo-voltaic (solar cells)

Simply explained Solar cells also referred to as PV cells, convert sunlight directly into electricity. The PV term is derived from the process of converting light (photons) to electricity (voltage), thus PV. This is not new technology as it was discovered in 1954 by scientist employed at Bell Telephone, who discovered silicon, an element found in sand, created an electrical charge when exposed directly to sunlight.

In the overall scheme of things a PV system is not really particularly complex considering its tremendous impact on our daily lives. Did you realize calculators and watches are powered by this system? First, panels collect the sunlight and turn it into electricity. The DC current is fed into an inverter which converts the DC into AC power, which is what powers your home. Doesn’t take a rocket scientist to follow that logistic.

Basic list of PV system elements:

Panels: PV panels, are your biggest expense as they can run anywhere from $2.45 to over $5 per watt. It can not be emphasized enough, proper placement and mounting is the single biggest thing that can affect the efficiency of the system. Poor location and mounting … poor performance.

Mounting equipment: As previously stated, it’s imperative the location of the panels, calculated to be exposed to sunlight the maximum amount of time over the period of a year, is checked and double checked. Once the location is verified, the real problem is securing the panels with enough integrity to remain in position for 25-30years. It does little good to sweat blood arriving at the utmost pinnacle of efficiency to position the panels, only to have them move due to poor installation techniques or material. Like buying a $100,000 RV with 1 gallon of gas in the tank. Looks good, but totally useless for its intended use of traveling.

DC to AC Inverter: This equipment takes low-voltage, high current signals from the PV panels and converts it into 120VAC (240VAC is also available) which makes it compatible to household appliances & etc. This equipment is the weak link in the system from the reliability standpoint, so don’t sacrifice quality for costs. You’ll regret it later.

 

Tracking Mounts: These mounts move the PV panels, mechanically, over the course of the day so they are directly exposed to the face of the sun, maximizing power production. Dual axis trackers change both azimuth and elevation, while single axis trackers only change azimuth. It depends on many variables which type would be the more beneficial for your use.

Azimuth is an arc of the horizon measured between a fixed point (such as true North) and the vertical circle passing through the center of an object usually in astronomy and navigation clockwise from the north point 360 degrees.” Webster Dictionary

If your like me … you really didn’t understand that explanation, but I include it because someone will.

Disconnect switches: Must be easily accessible and within reach of the smallest family member, and every member must know how to operate it. If any abnormal behavior occurs with the home’s electrical system, immediately disconnect the solar system. Why? Because odds are if something has malfunctioned and has created a safety hazard, it most likely will be the new installation, not the established house electrical system.

Utility power meters: Always notify your local power company that you are going to use a solar power electrical system. Why? Conventional power meters can spin backwards, but most companies will convert your power usage to a TOU (time-of-use) rate structure. It’ll save you a hassle of getting your electric bill correctly formulated.

Use Your Head:

Solar energy, although great, is too expensive to try the old trial and error method of design and installation. Don’t lose sight of energy efficiency being the most cost effective method of reducing the cost of heating and cooling your home. Do your due diligence and work with contractors who have demonstrated their expertise in building and remodeling to energy efficiency. This is especially true when switching to solar from a traditional power source. Get a Home Energy Audit before doing anything. It may offer options that will make conversion, for cost benefits only, unnecessary. It’s up to the individual, but installing any system that will require 30 years to pay for itself is a questionable choice.

basic-thermosyphon-water-heating-system

Basic Thermo – syphon system

Let’s assume you’ve had a Home Energy Audit performed and with a few changes to the homes windows and insulation, the cost of going solar is questionable, right on the edge of smart or wasteful. You want to do something. What about a solar water heater? Water heaters, especially older non-energy efficient types, are an energy consuming beasts.

How solar water heaters work: These systems are comprised of storage tanks and solar collectors, which use the sun to heat either water or a heat-transfer fluid in a collector to provide hot water to the house. The most common system utilizes a well-insulated storage tank to hold and maintain hot water. There are two types of solar water heating systems; Active direct circulation which require circulating pumps and controls, and Passive, which don’t.

Direct-circulation systems circulate water through the collectors and into the home, which can be used in climates where a freeze is uncommon. Indirect-circulation system pumps a non-freezing heat transfer fluid through the collectors and into a heat ex-changer, which heats the water that then flows to the home. These are used in cold weather climates.

A Passive Solar Water Heating System is typically less expensive than active systems, but not usually as efficient. But … the passive system may last longer. There are essentially two basic types of passive systems.

Integral-collector-storage: These systems can only operate in fair weather environments where it rarely freezes, and there is significant sunny daylight.

Thermo – syphon systems: The collector must be installed below the storage tank elevation in order for the warm water to rise into the tank. They are normally more expensive to install than the Integral-collector.

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Storage Tanks & Solar Collectors:

Solar water heaters will require a well-insulated storage tank, which has an additional inlet and outlet connected to the collector. There are 2 tank systems which include a traditional type water heater, as the solar heater will preheat the water before being pumped to the traditional water heater tank.

***Note*** Nearly all solar water heating systems will require a back up system in order to compensate for unusual high demand or cloudy days.

Questions to Answer Before Purchasing a Solar HW system:

1. Arrive at a firm estimate of the cost and energy efficiency of the particular system. The last thing you want is a $1000 increase surprise in the middle of installation, or a system that falls far short of expectations.

2. Evaluate the site’s solar resources. Some building lots, or current home location, is just not suitable for enough exposure to sunlight to provide the energy required without expensive modifications or unchangeable natural hindrances.

3. Double check the required size of the system. Some contractors, whether by inexperience or by deceit, will offer a less expensive system claiming it’s plenty big enough to do the job, but is totally inadequate. It’d be like buying a car with a little bit of brakes. Not a good idea.

4. This may actually be the first step you need to take. Check local codes, covenants and regulations which may prohibit you from installing a solar system. Usually, other than the cost of building permits, local governments rarely pose a problem. However, belonging to a homeowners association, or something similar, may prohibit any “unsightly” additions to a property. That’s an ambiguous term which can create unnecessary headaches and legal fees.

Screen Your Contractor:

Few people realize that a “Licensed Contractor” simply means the contractor paid a fee to the municipality to do business within its borders. It is no guarantee the contractor knows what they are doing. Ask questions and expect plain forth right answers.

1.What experience do you have installing and maintaining solar systems? Ask for referrals or site locations of finished jobs. A contractor proud of his work will welcome the opportunity to display its workmanship.

2. Does the company have experience installing the type of system you want? Solar systems have a general operating principle, but no two systems are identical. Are they capable of handling unexpected problems, such as hitting rock 8 inches down where there wasn’t suppose to be any.

3. Years of experience is a factor to consider, but don’t let that stop you from hiring a newer contractor. The new guy may be excellent and has a burning desire to begin a reputation of quality service, while the guy with 5 years experience may have performed shoddy substandard work, skating from one scam to another. Check your BBB.

We have only scratched the surface of understanding the many types of solar systems available, and they improve and become less expensive as time goes on. I just wanted to expose you to a few basics of solar water heating and its principles.

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