This web site will show you how to live lightly on the Earth by using solar energy. Our mission is to accelerate the transition to solar energy.
How to Use this Web Log
1. Browse through articles by clicking on "Older Posts" below each article in the center column. 2. Search through the Blog Archive at the lower right-hand column. 3. Read Editor's articles to the right. 4. Get Technical help in the lower left hand column. 5. Efficiency and low-waste strategies in the lower right column.
Friday, May 15, 2009
Solar Workshop Notes
Light On The Earth
The Solar Option
Can We Live Lightly on the Earth?
•Combustion of fuel and depletion of resources are the foundation of our economic prosperity and high standard of living.
•The Industrial Revolution - A cauldron of unintended chemistry and the decimation of the natural world.
•Can we have prosperity and a high standard of living some other way?
•Yes, if we want to, we have the technology to live in balance with the eco-system.
•The only question is:
Are we capable of changing our habits to preserve the natural world and to have enduring prosperity?
That is our Choice.
The Solar Option We have light on the earth. Let’s use it.
With up to a 40 year life, solar-electric panels are the most durable, low maintenance and reliable technology ever devised by man. And with no moving parts!!
How many products in your house have a 25 year warranty? Solar-electric panels do.
But, Isn’t it too expensive?
•Not if we design the systems wisely!
•The system I live on cost less than the price of a three year old, used economy car.
•Yet I have all of the modern amenities.
•I expect the system to last up to 40 years.
•I expect far greater reliability than the power grid.
•Energy security is a side benefit.
What are the three pillars of a practical solar energy system?
•Solar energy technology
Why Efficient Equipment?
•Constant efficiency improvements in energy-using equipment allows us to get the desired result with ever smaller energy use.
•Appliances, lighting fixtures, tools and systems can use a large or small amount of energy to perform the same function. Of course less is better!
•Added bonus: as a rule, the less energy an appliance uses, the longer it will last.
•The less energy you need the smaller and less expensive your solar energy system will be.
Low Waste Strategies
•Our waste of energy must come to an end.
•We may be wasting as much as 50% of the energy we use.
•Leaving energy appliances running when they are not being used cannot be tolerated. This means participation by every person in the household and the use of switches and timers to prevent waste of energy.
•A change in habits is a small price to assure the health of the natural world!!!
Reduce energy use through Efficiency
Products are labeled with their energy use
•Specified in watts
•Specified in watts/unit time
•Specified in voltage and amps which can be multiplied to approximate watts
•Can be directly measured during use with a Kill-a-watt meter
Calculating energy efficiency
•If you start with a given amount of energy, efficiency describes what percentage of the energy actually performs the desired function and what part is wasted.
•If an appliance is 80% efficient that means that 20% is wasted.
•In a calculation you can multiply by .80 in order to get 80%.
•For instance, a refrigerator of 20 cubic feet that requires 1000 watt/hours per day is more efficient than a 20 cubic foot modelthat requires 2000 watt/hours per day.
•The first model requires:
1000wHr / 20 cf =50 wHr/cf/day
The second model requires:
2000wHr / 20 cf =100 wHr/cf/day
What is a solar energy system?
•Electrical generation using solid-state (no moving parts) photovoltaics with solid-state electronic conditioning devices and electrical energy storage
•Thermal Solar (heating) devices to heat water and air, to dry clothes and foods, as well as cooling by evaporation.
•Solar technology can reduce the use of polluting forms of energy use by 80-95%.
How to reduce energy requirements
•1. Efficient equipment
•2. Reduce waste by use of switches, timers and a frugal energy ethic.
•3. Reduce energy use procedures starting with the most energy intensive appliances.
The Order of Energy Intensivity
1.Space heating and cooling (furnace/air conditioning)
11. Small electronic devices (cordless phones, rechargeable digital cameras, cell phones, etc)
Energy type in order of value
•Electrical Energy – Has a higher cost to obtain but is more useful because of its speed of transmission and ease and length of storage. It can be converted to a wide range of uses.
•Heat Energy (below the boiling point) is more readily available and easily collected but it dissipates rapidly. It is not economically convertible to electricity.
Solar heating and cooling utilizing passive solar and ventilation
Insulation, calking and ventilation
•These are cost-effective ways to reduce the amount of energy needed from expensive active equipment.
•Double or triple glazed windows reduce heat transfer through window glass.
•Insulation in roof floor and walls minimize heat loss or buildup.
•Calking reduces drafts and leakage of heat.
•Ventilation adds temperature control as it allows cool air to be pulled in down low as heat is expelled up high.
•Active or automated ventilation utilizes sensors, fans and mechanized closures and allows heating and cooling functions to be controlled without human input.
•The biggest bang for your buck!
•On average the 2nd biggest energy user in your household.
•Normal hot water systems use one component – a heater/tank utilizing electricity or gas to heat the water.
•A solar hot water system adds a few components to dramatically reduce energy cost. Thus there is a rapid payback.
What about cloudy weather?
•Solar energy creates heat when light strikes a dark surface. Higher energy visible wavelength excites the dark surface which then radiates a lower frequency, non-visible light called infrared. Infrared is heat.
•A hot water system is sized for cloudy conditions. Since solar does not always provide enough, a practical system also uses backup in the form of electric or gas.
The simplest system is best.
•Roof or ground mount?
•Pump or thermo-siphon (uses no pump)?
•Proximity to point of use.
•Type of backup
Flat plate collector
•The simplest and most economical form of solar water heater.
•The simplest, most elegant design.
The most durable and efficient system
•Ground mount gives easy access for occasional cleaning
•Allows close proximity to point of use
•Allows a simple thermo-siphon system with no pump to break down.
•Less plumbing, means less costly installation and no holes in the roof to leak.
•Instantaneous hot water heater is the best.
•Solar acts as a pre-heater reducing energy use.
•Extremely cost effective.
Heating air with solar energy
•Very cost effective
•Simplest form of collector
•Heat living space or the intake air to a clothes dryer.
•Allow the house to be the solar collector.
•After hot water, it is usually biggest energy user.
•Keep refrigerator in a cool place!!!
•Use Energy Star Appliances for best performance to cost ratio.
•Use a 20 Amp appliance timer on your fridge for reduced energy use.
•Avoid high-cost solar specialty refrigerators. They cost too much and are harder to get repaired.
•Keep it full to store the cold.
•Uses quite a bit of energy per unit time.
•Pressurizing water pumps are only used when water is running and so use less.
•Washing machines use pumps which partially accounts for their relatively high energy use.
•Small pumps like those for aquariums use relatively small amounts of electricity but are sometimes on 24/7, so it adds up.
Washer and dryer
•Laundry equipment is fairly energy intensive.
•Use Energy Star appliances
•Use liquid detergents, cold water and short wash cycles for most applications.
•Use a solar assisted gas dryer in a solar electric house.
•Use compact fluorescent or LED lights whenever possible. Use compact fluorescent bulbs that have globes to avoid mercury contamination.
•Avoid lights that are hot to the touch. This indicates low efficiency.
•Do not leave lights on when they are not required.
Energy consumption of light bulbs
•The larger the set the more electricity it uses.
•A 32 inch LCD flat screen TV uses about 100 watts
•A 24 inch model uses 60 watts.
•Standby mode uses a lot of energy.
•Eliminate these parasitic losses with a switchable power strip.
•My solar energy system has no problem handling the occasional use of power tools.
•Table saw, circular saw, chop saw, drill, rechargeable tools, sanders all operate without a problem.
•Same is true of most kitchen appliances.
Computers and printer/scanners
•Laptops use much less energy than desktops.
•My laptop uses about 20 watts compared to up to 250 watts/hr for a desktop computer.
•Some larger laptops use up to 90 watts/hr.
•Printers/scanners use a very small amount of electricity. But they have standby energy use. Use a power strip to completely shut it down when not in use.
Desktop vs. Laptop
•Based on two hours use per day:
•Annual Desktop energy usage: 500wHr x 365 days/year = 182.5 kwHr/year
•Annual Laptop energy usage:180wHr x 365 days/year = 65.7 kwHr/year
•Energy Savings by using a laptop 182.5 kwHr – 65.7 kwHr = 116.8 kwHr/year
•By reducing your use 116.8 kwHr/year you require approximately 90 watts less of solar generating capacity. At about $8.00/watt installed, this amounts to $720 less solar generating equipment.
•All work well with solar since their use is occasional and total energy use is low over time.
The Photovoltaic (PV) Electrical Generation System
•Electricity generated from light
•Proportional to the amount of light
•1000 watts/square meter on a sunny day
•PV panels are from 15-22% efficient
•Crystalline and multi-crystalline varieties
•The best have a 25 year power warranty
•The most durable active product devised by man with an expected life of up to 40 years
•100-300 peak watts per panel
•High-watt panels are physically larger but heavier and harder to handle
•Smaller panels are easier to handle but require more connections and more installation expense
•If your system is connected to the powergrid and can sell power to the electric company it is called a grid-tied system.
•If your system does not sell power to the grid but is independent or is connected but only uses the grid power as backup, it is called an independent system.
•A hybrid system has elements of both types
Grid-tied vs. Independent System
Independent System Components
The difference between the two types of system
•Used properly they have 90%+ efficiency and a 10-15 year life.
What to expect from batteries
•As an example, I paid $1200 for my batteries that give me 5-10 KwHr of storage at 90% efficiency.
•I expect them to last at least 10 years. That is a cost of about $10 per month.
•There are new batteries in development with 1/10th the weight, 1/5th the cost per kwHr and that could last up to 40 years. They have a claimed 95% throughput efficiency and are completely no-maintenance and environmentally friendly.
•By the time your first set of lead-acid batteries is used up, these new types should be available.
•Batteries require periodic addition of distilled water.
Direct Current (DC) vs. Alternating Current (AC)
•Normal household current is AC
•DC is generally used in boats and recreational vehicles and is stored in batteries
•AC appliances are more durable and readily available
•The inverter changes the DC from your panels into AC for your house.
How much energy is available from the sun?
Variation during the day
Average Annual Variation
Average retail price per peak watt of PV panels
•PV panels are sized to their peak output capacity.
•On a clear day at , if the panel is perpendicular to the sun’s rays, it should put out an amount in watts that is very close to the rated output of the panel.
•The actual output varies with panel mounting angle, cloud cover and time of year (length of day)
How panels are mounted
•Fixed-angle, roof Mount
How panels are mounted
•Fixed-angle, ground mount
How panels are mounted
•Sun-tracking, ground mount
The best mounting system
•Panels and all other components mounted together
Benefits of mounting everything in one location
•Lower cost of wiring and less losses in the wiring
•Ease of access and maintenance
•Ease of access reduces cost of repairs
•Ease of maintenance reduces cost of maintenance making it more likely
•Lower overall installation cost
•Does not interfere with or penetrate house roofing system
•All solar panels must be cleaned on a regular basis. At least every 3 months. Don’t believe anyone who says they are self cleaning!!
•This means using a soft broom to clean the surface and rinsing with water. Not so easy if the panels are on an inaccessible roof.
Maintenance issues, cont’d
•Not so easy to clean or inspect if panels are put together in a huge array with no space between panels for access.
•If you must roof mount, something like this makes more sense.
The problem with roof mounting
•The fasteners that penetrate the roof are a cause of possible roof leaks (40 years is a long time).
•To replace the roofing will require the complete dismounting of your solar panels.
•In the event of a house fire the firemen wanting to make an opening in your roof to save the house make have to destroy your solar panels.
•Cleaning and repairs are more difficult on the roof.
Designing system for long life
•Photovoltaic systems last 30-40 years
•Any system with that kind of life expectancy must be designed for ease of use, low cost of maintenance and repairs
•An improperly designed or installed system can cause what should be a trouble-free technology to become just the opposite
Monitoring your independent system
•In normal use, you only need to monitor one number, the DC voltage.
•This meter must be mounted in a highly visible location like the kitchen
What type of meter?
•LED meter with 3/4 to 1 inch numerals
•Mounted in central location such as the kitchen
•Always visible even in the dark
•Two digits to the left of the decimal point gives the range of sensitivity necessary
•By observing how this number responds to energy use you will learn how your system works and will have early warning of any malfunctions
•One inverter per panel allows remote monitoring and assessment of each panel’s performance over time. This maximizes the output of your panels.
•Micro-inverters generally have a longer life expectancy due to minimal heat dissipation.
•Other inverter systems may have similar monitoring systems.
•These devices control the output of the PV panels.
•On an independent system they control the charging of the batteries and include multiple monitoring functions.
•On grid-tied systems they are included as a part of the inverter and maximize the power obtained from the panels.
Inverters and inverter/chargers
•Inverters are electronic devices that change Direct Current (DC) electricity into Alternating Current (AC) electricity.
•Life expectancy is 10-20 years
•Warranties are from 2-10 years
•Continuous output in watts
•Short-term surge capacity
•Input (DC) voltage
•True Sine Wave or Quasi-Sine wave
•Company reliability in the marketplace
•Monitoring and trouble shooting features
Backup For Independent Systems
•Use the grid with a battery charger (least expensive if you are already connected).
•Use a generator in an enclosure with an inverter/charger.
•Automated vs. Manual operation
Using Peak Sun Hours to Size Your System
•Peak sun energy occurs between and on a cloudless day. This is one peak sun hour.
•The annual average daily number of peak sun hours is different in each location depending on latitude, cloud cover and elevation.
•This information is available on charts and allows estimates of expected energy availability for sizing a solar system.
•You can further refine this chart by estimating your energy-use habits. If you are careful in the way you use energy, these figures will work well. If you are an average householder, you can add 15% to these figures. If you don’t pay any attention to how you use energy, then you can double these estimated system costs.
•Which demonstrates conclusively why energy efficiency and low-waste strategies can pay off in a big way.
•These estimates of cost do not include the tax credits available from State and Federal government.
•Tax benefits can reduce the overall cost of the system by 30% or more. U.S. Tax incentives can be found here: