Colorado Energy Master Program Colorado State University Extension CSU Extension Consumer Energy Team Solar Energy for Colorado Consumers Kurt M. Jones, County Extension Director, Chaffee County (April, 2014) Learning Objectives: Evaluating the Solar Resource o Technical feasibility, permitting & zoning considerations How Solar Technology Works o Types of systems and equipment used Sizing Solar Systems o Evaluating electric and hot water loads o Determining offset Financial Feasibility o Financing options, incentives, calculators Case Studies Trends Sources of Additional Information Evaluating the Solar Resource Introduction Colorado enjoys copious amounts of sunshine, estimated at 300 or more days each year. This, along with our low relative humidity and high elevations makes solar energy an important renewable energy resource. Many renewable energy technologies such as wind energy can be sporadic and not ideal in most locations. Solar energy, however, can be easily measured and seasonal differences can be tracked. Provided the proposed site has adequate exposure to the South, East or West, solar energy may be warranted. Today, solar energy is used in electrical generation and solar thermal (domestic hot water and space heating) applications. Today s class will introduce these technologies and offer suggestions about where they may fit into the homeowner s or small business energy needs.
Solar Radiation Basics It can be confusing to understand the differences between power and energy. Power is a measurement of the rate of energy. For example, a watt or kilowatt are measures of power. When you have power for a given amount of time, this is a measurement of energy. Energy is the ability to perform work. For example, a kilowatt-hour (kwh) is a measure of energy. Another way of looking at this: Energy = Power X Time A common mistake is to use power and energy interchangeably. If you were asked, How much energy comes from an 80-watt solar panel? you would be unable to answer this question. The correct answer would be, It depends on how much sunlight is exposed to the panel and for how long. In the solar industry, we use terms such as solar irradiance (1,000 W/m²) as a measurement of power, and solar insolation (5.5 kwh/m²) as a measure of energy. Other measurements useful in solar applications include: Power Energy Joules/second = Watt Joule BTU/hour (BTUH) British Thermal Unit (BTU) Therm = 100,000 BTU 1 Kilowatt = 1000 watts Kilowatt-hour (kwh) Peak sun hours are those which produce power at or above 1,000 w/m². As a general rule of thumb, these hours are between 9:00 am and 3:00 pm (also called the solar window). During these peak sun hours, designers will look for potential shade objects as this will affect the total energy output from a system. Irradiance can be measured at a given site using an irradiance meter. Insolation data is normally found in published tables which gives regional data, or (more likely), downloaded from the National Renewable Energy Laboratory (NREL) website via an online calculator called PV-Watts. This tool is discussed in further detail later. It is important for designers to understand how the sun will track throughout the year; fortunately this is predictable. How the sun travels across the sky in a given location is based on its latitude. In Colorado, our latitude ranges from 37 degrees North along the New Mexico border to 41 degrees North along the Wyoming border. Understanding this fact has allowed the solar (and greenhouse) industry to develop tools for evaluating the sun s path and evaluate shading potential at particular locations. Sun path charts are available from the University of Oregon. Their Sun Chart Program allows the user to go to their website (http://solardat.uoregon.edu/sunchartprogram.html) and
download a map of how the sun will travel for a given latitude/longitude, or via postal zip code. This data, along with a compass, protractor, and plumb-line, can allow the user to conduct an analysis of a potential site. See Solar Site Analysis handout for more details. Solar designers have tools which speed up this process. Many use the Solar Pathfinder to track the sun s seasonal path, identify shading issues such as buildings, trees, overhead utility lines, etc. The Pathfinder can also help estimate energy losses from shading, useful for solar thermal applications and critical for photovoltaic applications. It can also be adjusted to account for magnetic declination to determine array azimuth. The Pathfinder varies in price, but runs about $275-300. Software is also available for use with the pathfinder to aid in design for an additional $230. The sun s apparent location in the sky as compared with true south is called the azimuth. Related to azimuth is the location of the magnetic field in relation to the Earth s axis. Because the magnetic field is not aligned with the axis, we utilize a correction factor to determine true south. In Colorado, this correction factor ranges from 10 East of South along the Kansas border to 13 East of South in NW Colorado. I typically use 11 East of South as an average reference, and insolation does not change dramatically within 2-3 of error. For most applications, the greatest amount of energy comes from a solar array which is oriented due (not magnetic) south (array azimuth = 180 ) that is not impeded by shading. Array tilt is the next determination for the solar designer. For maximum energy, the panels in the array should be perpendicular to the angle of the sun s rays. In general, this tilt is at latitude for Spring and Fall, at latitude plus 15 for Winter, and at latitude minus 15 for Summer. Some photovoltaic systems can be designed to be adjustable to take advantage of these seasonal differences, while others (and solar thermal arrays) are fixed with the understanding that at times of the year, power produced will not be at the maximum. Tilting the array at latitude for fixed applications will give the best energy output year-round. Some photovoltaic arrays can be mounted to single-axis trackers or dual-axis trackers to help maximize power production. Single axis arrays are oriented North/South and track the sun s path across the sky each day from East to West. Dual-axis trackers are oriented more due south, but can track the sun both daily (east to west) and seasonally. Careful consideration should be given to whether the added costs (purchase, installation and maintenance) of a tracking system are justified by the increased energy produced. For fixed systems, the designer needs to determine the design month. If the demand (load) is consistent throughout the year, the designer will often use the month of the least insolation. If the load varies, the designer evaluates the monthly loads and designs the system to meet the peak load month. Grid-tied photovoltaic systems utilizing net metering will often use the average annual insolation for their design parameters.
For assistance with determining insolation values for design month, most designers will turn to NREL PV-Watts. The current version is version 2 which allows for location-specific data (based on lat./long. or zip code), but version 1 is still available. Version 1 made the user choose data from Eagle, Alamosa, Pueblo, Colorado Springs, Grand Junction, or Boulder for analysis. The designer had to determine which locality had environmental conditions similar to design site. For example, one solar designer in Salida used Colorado Springs data, another used Alamosa data (personal preference for each). Permitting & Zoning There are numerous permitting and zoning and perhaps covenants restricting solar installations. There are also numerous protections available to insure continued access to solar energy for existing systems. Upon review of regulations available online at the Colorado Energy Profile website (http://www.energyincolorado.org/) regarding solar energy, there are 110 policies in place regarding renewable energy, 43 of which deal with solar. The Laws & Policy s Database is a keyword searchable database. Of interest to solar customers is solar easements (C.R.S. 38-32.5-101 et. seq; Laws 1979, S.B. 133) which states: These provisions detail the requirements for establishing solar easements, defined as "the right of receiving sunlight across real property for any solar energy device." A solar easement be in writing and its conditions described in detail. The provisions expressly prohibit the creation of solar easements by prescription and require that any conditional grant of a solar easement or any condition of termination be set out in writing. Provisions for compensation of benefited and/or burdened property owners, if any, must also be set out in writing. Solar systems, whether photovoltaic or thermal, require a permit. Photovoltaics are regulated through the State Electrical Board, solar thermal is regulated through the environmental health department. Check with your local building department about pertinent permitting requirements. There may also be sales and use tax exemptions for renewable energy equipment, and property tax exemptions depending on the jurisdiction of the home. Visit with your local county assessor s office for more information. A good place to search for applicable incentives, http://www.dsireusa.org lists most of the incentive programs available. Some additional considerations for site analysis include checking into any covenant restrictions or being cognizant of view sheds. Roof-mounted solar systems also require the roof to be in good repair (otherwise, complete the roof work prior to installation).
How Solar Technology Works For purposes of the Colorado Energy Master Program, we will be discussing basic Solar Thermal technologies including domestic hot water, space heating and snow melt applications. We will also be discussing solar photovoltaics for grid-interactive and off-grid applications. Finally, we will touch on passive solar design, but not go into a lot of detail. Though there are concentrated solar thermal and photovoltaic applications, this is beyond the scope of this course. Solar Thermal Applications There are numerous solar heated hot (warm) water systems and variations available. This section will introduce some of the more common ones. Batch system utilizes a large volume of water that is exposed to solar radiation. Because the collector and storage are the same unit, there is no level of frost protection. Some variations of the batch system are incorporated in some greenhouse applications for temperature moderation. Batch systems are simple in their design, but suffer large heat losses in inclement weather and overnight. Thermosyphon systems have a separate collector located below the storage tank. Heated water rises through convection through the collector and is stored in the tank located above the collector. Similar to the batch system, there is no level of freeze protection, but thermosyphon systems can retain heat better than their batch system cousins. Pool heating collectors are simplistic in their design and plumbing. The collectors are unglazed and un-insulated. These may be found in temperate locations in the United States on roof tops where water from the recreational pool is pumped through the collectors, is heated by the sun, then is returned to the pool. The pool becomes the heat storage for the collectors. Assuming the pump is turned off during inclement weather and overnight, very little heat is lost through the collectors. Again, no freeze protection in this type of system. For climate such as in Colorado, the types of solar thermal systems that would be used would be drain-back systems and closed-loop glycol systems. These offer adequate levels of freeze protection, making them the most commonly installed systems. Drain-back systems utilize a controller which switches on a circulation pump to fill the collector with water. The system circulates water throughout until the temperature difference between the collector and the incoming water is less than a pre-set limit, switching off the circulation pump. When the pump is off, the collector and all the plumbing drains back into conditioned (heated) space. Freeze protection approaches -20 F with this type of system, provided all of the plumbing and collectors are mounted on an incline to allow the system to fully drain back when the pump is not running. Another concern with these types of systems is that they utilize a drain-back tank which is exposed to the atmosphere, and water splashing can be heard with this type of system.
Closed-loop glycol systems do not mix with potable water. Instead they transfer their collected heat through a heat exchanger. The system (collector and associated plumbing) is filled with a mixture of propylene glycol (non-toxic) antifreeze and water, and remains pressurized. The circulation pump for the collector loop runs whenever the fluid level in the collector reaches a pre-set limit, or can run off of photovoltaic power (DC-powered pump). A second circulation pump sends water from the water-storage tank through the heat exchanger and back into the storage tank. This pump is run off a controller which determines changes in temperature ( T controller) desired in the system. Closed-loop glycol systems are the most common used in the United States, but may require periodic maintenance. One drawback on these systems is that if the propylene glycol gets hot, it can turn acidic and start breaking down copper piping within the collector, heat exchanger or related plumbing. It is important that this fluid circulates whether there is a call for hot water or not to avoid this acidic reaction. Frost protection for closed-loop glycol systems can reach -50 F. Types of solar thermal collectors There are two basic types of collectors used in solar hot water systems. The flat plate collector is comprised of flow tubes and plumbing manifold encased in a collector housing. From the back to the front, there is a back plate, insulation, absorber plate, tubing, and tempered glass cover. These collectors work well for both drain-back and closed-loop systems, have a long lifespan if maintained (30+ years), and are more efficient in high-light and moderate to low heat situations. Probably less expensive than evacuated tube collectors (depends on copper prices). Drawbacks for these types of collectors include weight (empty weight of these collectors can range from 80 pounds to 150 pounds, and maybe 10-15 pounds more filled), and potentially poor aesthetics. The evacuated tube collectors have a plumbing manifold located at the top with a series of individual air-evacuated tubes which connect into the manifold. The tubes operate in a vacuum of air surrounding the absorber plate. Heat collected in plate rises and interacts with fluid passing through the manifold. Tubes are efficient (can actually hold tube with bare hands in full sunlight) at transferring heat. These are gaining popularity in that they are attractive (look modern ), and are easier to install than flat plate collectors (can carry individual tubes up ladder to roof and install in place). The tubes can also be turned to correct for azimuth for roof mounted systems. Good choice for lower-light situations or high-temperature water loads. Drawback is that they will not shed snow as quickly as flat plate collectors, and longevity is not as good. Tubes which lose their vacuum will need replacement (estimated at 15 years). Balance of Solar Thermal System Components Beyond the collector, water storage is the most important component of the solar thermal system. The amount of storage needed depends on the square footage of collector. In Colorado, it is recommended to have 2 gallons of water storage for every square foot of collector. For example:
2 SunEarth EC-40 colectors (41 ft.² each) would require a minimum of 164 gallons of storage = 2 80 gallon tanks plumbed parallel (80 gallon tanks are a common size less expensive) Evacuated tube collectors can get by with fewer storage gallons per square foot. Common pressurized tank sizes are 40, 50, 80, 120 gallon. For systems requiring more than 240 gallons of storage, unpressurized tanks may be needed. Storage water stays in tank, potable water flows through heat exchangers as well as thermal fluid (water or glycol) can flow through separate heat exchangers. Drain-back systems can empty directly into tank without exchanger. Water circulation pumps control water (or glycol mixture) flowing through collectors or between storage tanks. These are regulated by controllers which read temperature gauges (probes). Water temperature tempering valves are also installed to reduce potential for water scald. Building codes will also likely require backup heating (or the mortgage lender) heating sources which can include modulating boilers (think on-demand water heaters) or electric elements within a pressurized water storage tank. Finally, the designer will plan plumbing runs with solenoid valves depending on the complexity of the hot water load. In-floor heating systems in combination with domestic hot water loads add to the complexity of the solar system. Photovoltaic Solar Systems Photovoltaic solar panels convert solar radiation into Direct Current (DC) electricity. When referring to electrical generation, insolation is described at watts per square meter. Photovoltaic solar systems typically contain several panels wired together (termed an array), electrical disconnects, over-current protection (circuit breakers or fuses), inverter, junction box, and other specialized equipment depending on application (grid-tied, off-grid, battery-backup). Photovoltaic solar systems can be either wired into the electric utility grid ( grid-interactive or grid-tied ) or can be independent of the electric grid ( stand-alone or off-grid ) by storing DC electricity in several batteries wired together (battery bank). Balance of PV System Components Everything that does not constitute the solar panels themselves is termed the balance of system. These include electrical disconnects, over-current protection (circuit breakers or fuses), inverter, junction box, system grounding, batteries, charge controller, etc. Systems can be roof mounted (typically on a system of rails), ground mounted, or pole mounted, and numerous racking systems are available to assist the solar designer. Roof mounted systems are supported by the structure they are mounted to, so the roof needs to be in good repair. If roof repair work is needed, it should be completed prior to installation of a solar system.
Ground mounted and pole mounted systems will need an engineered footing and pole or other racking system for its support. Snow loads and more importantly, wind loads need to be accounted for in designing the footing and structure. System designers must also calculate the extreme conditions these systems may face and size their electrical components accordingly. PV systems function best at extremely cold temperatures, so systems are designed to handle this load based on historic low temperatures. Wire is also sized according to the extreme heat it may face within conduit and without losing more than a 3% voltage drop. System designers and electrical inspectors understand these parameters, so the customer does not need to worry about this aspect. As previously mentioned, PV systems produce DC electricity, however household appliances are designed to utilize alternating current (AC) electricity. Converting DC electricity to AC electricity requires the installation of an inverter(s). Inverters not only convert DC to AC electricity, they can also sense power outages from the electric grid and automatically shut off the flow of electricity from the solar system as a protection to utility workers. Finally, they can sense a ground-fault condition where grounded elements are carrying electricity and shut off the system. For example, damaged PV panels may short-circuit, causing a ground fault. Off-grid systems require additional important pieces of equipment. A charge controller will control the flow of electricity into the batteries from the PV panels (preventing overcharging), but can also sense when the batteries are getting dangerously low on voltage and can shut off the system to protect the batteries. Electricity is stored in several batteries wired together, and the batteries are stored in a battery box. Batteries are typically lead-acid, but can also be sealed gel-cell or absorbed gas mat as well. Lead-acid batteries can emit hydrogen gas as batteries reach full charge, requiring the use of a battery box. Because hydrogen gas is explosive, no open flames can be near liquid lead-acid batteries! Some additional applications for PV systems beyond grid-tied or off-grid household use include solar water pumping (see Fact Sheet 6.705 Solar-powered Groundwater Pumping Systems) and low voltage lighting applications such as parking lot lighting, roadside signs, and others. Typically these applications utilize DC-powered lights/pumps, and may or may not utilize batteries depending on the application. Sizing Solar Systems Sizing Photovoltaic Systems Choosing the size of a system needed depends on the type of system. Grid-tied systems are easier to size, as a customer can chose to offset part or all of their electrical usage. Off-grid systems need to provide all of the electrical demands, plus a buffer for periods of inclement weather (termed autonomy). Many off-grid systems will utilize a hybrid system with a backup generator, but relying on this type of electrical generation is expensive and noisy. Hybrid systems can also utilize other renewable energy sources such as wind turbines as a secondary source of electrical generation.
To size an off-grid system, you will first need to inventory your electrical demands or loads. The simple act of turning on the light switch or starting the microwave draws electrical demands that need to be accounted for. Typically, the load estimation will account for all electrical loads present (lights, appliances, etc.), the amount of time each day the appliance are used, and the number of days each week the appliance is used (weekend cabins do not use electricity every day, but have higher demands when occupied). An example of a Load Estimation Worksheet may be found online at http://www.ext.colostate.edu/energy/solar.html. By adding up the electrical load needs, inserting an autonomy factor, accounting for design inefficiencies (batteries can be 80% efficient, inverters can be 90% efficient), and any voltage drop due to long wire runs, a system designer can determine the size of system necessary for off-grid applications. To size a grid-tied system, electrical customers can add up their total electrical usage for the year (available on their utility bills), and divide by 365 days per year. This daily electrical usage (kwh) is then divided by the average solar resource (insolation) in their area. In Colorado, an average insolation factor is 5.5 hours per day. The result is the amount of kwatts needed in a solar array (not accounting for design inefficiencies). For example: A Colorado home had a total of 8002 kwh of energy usage for a year (example 08/2011). 8002kWH/365 days = 21.92 kwh/day 21.92 kwh/day 5.5 daily insolation = 3.985 kw = 4000W PV System 4000W.90 inverter efficiency = 4444W system = 4500W system There are also interactive calculators available for on-grid applications. Please visit http://www.ext.colostate.edu/energy/solar.html for links to several calculators. These calculators can give examples of costs for a system and applicable financial incentives. Another way to size a photovoltaic system is from the supply side. If the owner is limited to a roof-mounted system, you can calculate the size of the PV system based on the square footage of the available roof. PV panels can produce about 10 watts per square foot on average, so one can calculate the square footage of the roof space, reduce some of the roof space for installation/maintenance, then multiply by 10 watts. For example: South-facing roof measures 14ft. by 25 ft. 14 X 25 = 350 ft.² 350 ft.² X 71% = 250ft.² usable space 250ft.² X 10 watts/ft.² = 2500 watts or 2.5 kw system Sizing an off-grid system is a bit more complicated as the solar system has to provide 100 percent of the power, including during periods of inclement weather and at night (termed autonomy). The way to start sizing an off-grid system is to evaluate all the appliances, lights, etc. that use electricity in each room of the house, determine days of autonomy (normally 3-4
days), and size your battery bank to meet this electrical load. After determining the number of batteries needed, then the designer will size the solar array to charge those batteries during the design month previously discussed. An electrical load worksheet is available on the CSU Extension Solar website. Most off-grid systems will incorporate backup power from a wind turbine (if adequate wind is available), microhydro (if applicable) or most likely from a diesel-powered generator. Adding in the backup to the solar system allows the designer to utilize average insolation readings for the site instead of the lowest insolation (design month), and can lower the days of autonomy (from 4-5 days to 3-4 days for example). This lowers the size of the battery bank and lowers the size of the PV array, often making the hybrid system cheaper for the homeowner. There are added costs of operation of the backup system (diesel fuel/maintenance) which should be evaluated. A common misconception is that solar systems will not fully charge a battery bank which has been operating during autonomy on the first day of full sunshine. It will likely take several days to regain full charge following extended autonomy without utilizing backup power or reducing the daily load on the system. Sizing Domestic Hot Water Systems Sizing domestic hot water systems depends on the occupant s habits, in other words, the demand that the residents have on the system. As a general rule of thumb though, designers will use a standard of 20 gallons of hot water demanded per person, per day. The first step is to calculate the energy required to supply this demand. The formula used is: Energy= volume * density * specific heat * temp change Q = V * * C * T Here is an example of how this is used: Scenario: A family of 4 in Fort Collins conservatively uses 60 gallons of hot water daily. They have measured their incoming water temperature at 45 F, and desire a final temperature of 120 F. Their designer decides to use some flat plate solar collectors (SunEarth EC-40), and can mount these at latitude + 15 facing due south, and is assuming an efficiency of 85% due to lost heat in plumbing. Let s start with some ALGEBRA! Formula: Q = V * * C * T o Q = 60 gal * 8.33 lbm/gal * 1.0 Btu/lbm F * 75 F o Q = 37,485 Btu o Q = 38 kbtu Next we need to look at PV Watts to determine insolation values. PV Watts for Fort Collins (80521 zip) Best month Sept. 5.79 kwh/day Worst Nov. 4.51 kwh/day Convert kwh/day into Btu/ft² day Formula: kwh * 317 = Btu/ft² day
Best: 1835 Btu/ft² day Worst : 1430 Btu/ft² day Utilizing testing data on chosen panel (from owner s manual, utilizing Btu/ft² day): 44 kbtu/day in Sept 16 kbtu/day in Nov Factor in inefficiencies 44 *.85 (15% losses) = 37 kbtu/day 16 *.85 = 13.6 kbtu/day Demand is 38 kbtu/day Sept. - 1 panel = 97% of demand Nov. - 1 panel = 36% of demand Size water storage tanks 2 gallons of storage for every square foot of collector space 41 square feet for this collector = 82 gallons for one collector So for this scenario, they can offset their demand year round with one collector and 80 gallons of storage, or go with two collectors and 160 gallons of storage, fully meeting their demand in the summer/fall months and offsetting in the winter/spring months. Careful evaluation of the costs/benefits will help determine which scenario makes the most sense. Financial Feasibility Investing in a solar system is not an inexpensive endeavor. The thought of purchasing the next 20 years worth of electricity at one time can be daunting. Careful consideration of the costs and benefits should factor into the decision-making process. As with any renewable energy investment, best return on dollars is on demand side of the equation rather than supply side. Becoming energy-efficient is the first step in renewable energy. Solar systems can be expanded upon later, provided initial installation accounts for future expansion. There are a number of financial incentives for investing in a solar system. For grid-tied PV systems, there may also be incentives from your electric utility. A good place to search for applicable incentives, http://www.dsireusa.org lists most of the incentive programs available. For grid-tied PV systems, there is a tool that has been developed which can help analyze the financial investment. This is available online at http://www.ext.colostate.edu/energy/solarassess.html but you will want to do some homework before using this tool. Careful evaluation of the previous year s electrical demand (kwh) is needed, as well as how much was paid per kwh. You will also need to know about the proposed size of the solar system in watts, the installation cost per watt, any rebates offered by the utility company, and a completed PV-Watts printout of the system parameters (size, tilt, orientation, location) to know the expected kwh output of the system. Once this information is obtained, you can complete
the downloadable Excel spreadsheet entitled Photovoltaic System Financial Feasibility Calculator from the CSU Extension website. Evaluating the financial feasibility for off-grid PV systems is difficult for several reasons. First, there is likely not another alternative for comparison purposes. Next, one of the largest expenses for off-grid solar systems is the battery bank. How well that bank is maintained directly correlates to battery longevity, hence system longevity. Frequent replacement of batteries will add great expense over the life of the off-grid system. How much reliance on hybrid components will also alter the feasibility of the solar project. Poor estimation on days of autonomy can use the generator more frequently, potentially necessitating the replacement of the generator. Evaluating the feasibility of a solar thermal system is also complex. Most designers lean toward a cost/benefit analysis approach. In other words, the solar system offsets a certain number of Btu s (Therms) or kwh s, and the value of this energy is compared with the other heating fuel (propane, natural gas, electricity) value. These calculations can get pretty involved, so the payback period can be confusing. One way of comparing costs is outlined below: Electric Water Heater Natural Gas Solar Hot Water Annual Energy 4500 kwh 180 therms 4500 kwh or 180 therms Cost per unit $0.11 $1.25 0 Rate of inflation 6% 10% 3% Installation Cost $1,500 $1,500 $11,000 Annual Maintenance 0 0 $ 100 Cost to Operate Year 1 $495.00 $225.00 $ 100.00 Year 2 $524.70 $247.50 $ 103.00 Year 3 $556.18 $272.25 $ 106.09 Year 4 $589.55 $299.48 $ 109.27 Year 5 $624.93 $329.42 $ 112.55 Year 6 $662.42 $362.36 $ 115.93 Year 7 $702.17 $398.60 $ 119.41 Year 8 $744.30 $438.46 $ 122.99 Year 9 $788.95 $482.31 $ 126.68 Year 10 $836.29 $530.54 $ 130.48 Total cost of energy consumed $6,524.49 $3,585.92 N/A Total Cost after 10 years $8,024.49 $5,085.92 $12,146.39 Total Cost after 15 years $13,021.61 $8,648.81 $12,859.89 Total Cost after 20 years $19,708.87 $14,386.87 $13,687.04
In this scenario, the solar system payback for electric-offset is much faster than a natural gasoffset system. This type of table (used frequently in the field), can be a bit misleading as it assumes 100% offset of fossil-fuel system with solar-powered system. Reality is likely a mixture of solar and backup energy, making the spreadsheet much more cumbersome. Trends Solar technology (Photovoltaics in particular) is a rapidly moving target to be able to pinpoint future trends. Economies of scale (larger solar systems) will predominate the marketplace in the current and near future as solar electricity will approach parity with coal-fired electrical generation. For example, in March, 2014, THiNKnrg announced the lowest price power purchase agreement on record with Palo Alto's municipal utility, selling power for just 4 cents per kw-hr. The 398 kw project isn't large but it's a new benchmark for the solar industry in the future. First Solar broke ground on the 250 MW Moapa Southern Paiute Solar Project earlier this year (2014). Located just north of Las Vegas, the project will be one of the largest in the world when completed and provide enough power for 93,000 homes. Turning more locally, much debate has hinged around the value of net-metering. Utilities have argued that the current practice of kwh production credit for kwh produced (full credit for grid-tied applications) is poorly valued. The argument is that the actual value is not full retail credit, but net metering policies/laws forces full retail value for grid-interactive renewables. This could potentially have a significant effect on the financial feasibility of distributed energy production, and the small businesses this industry supports. Many utilities are reaching their required renewable energy portfolio standards, and many of the financial incentives for distributed energy systems are tailing off as a result. Though solar photovoltaic systems are becoming more affordable, much of this is due to financial incentives (whether a leased or customer-owned system). Current federal tax credits are set to expire in December, 2016. It is unclear whether these will be extended beyond this deadline. Though solar systems can be a depreciable asset for a business, many individuals count on the tax credits in the financial feasibility analysis of purchased systems. Innovation of manufacturing processes and materials will continue as demand remains strong for solar photovoltaics. Though still considered experimental, MIT developed a solar cell that averages forty percent efficiency, and will have a much longer lifespan than our current monocrystalline silicon, polycrystalline silicon, or thin-film photovoltaics. Innovations are also coming to allow for faster installations for professionals, better battery storage options, and
system components (for example, inverters will allow for emergency backup power without need for battery banks). Sources of Additional Information There are numerous sources for additional information. Exercise caution in evaluating sources of information to insure they are applicable to Colorado s climate and are of an unbiased nature. Websites CSU Extension Consumer Energy CSU Extension Solar Webpage NREL Solar Learning Page University of Oregon Sun Charts NREL PV Watts v. 2 http://www.ext.colostate.edu/energy/consumer.html http://www.ext.colostate.edu/energy/solar.html http://www.nrel.gov/learning/re_solar.html http://solardat.uoregon.edu/sunchartprogram.html http://www.nrel.gov/rredc/pvwatts/grid.html CSU Extension Fact Sheets 6.705 Solar-powered Groundwater Pumping Systems 10.624 Harvesting Energy from the Sun: Solar Photovoltaics 10.627 Introduction to Domestic Solar Hot Water Systems Reference Books National Fire Protection Association (2007) National Electric Code: NEC 2008. National Fire Protection Association, Quincy, MA. National Fire Protection Association (2010) National Electric Code: NEC 2011. National Fire protection Association, Quincy, MA. Ramlow, B. & Nusz, B. (2010) Solar Water Heating: A comprehensive guide to solar water and space heating systems. New Society Publishers, Gabriola Island, BC, Canada. ISBN 978-0-86571-668-1 Solar Energy International (2008) Photovoltaics design and installation manual. New Society Publishers, Gabriola Island, BC, Canada. ISBN 978-0-86571-520-2 Solar Energy International (2013). Solar Electric Handbook: Photovoltaic fundamentals and applications, 2 nd Edition. Pearson Learning Solutions, Boston, MA. ISBN 978-1-256-91816-5 This publication was written as accompanying materials for the Colorado Energy Masters program for Colorado State University Extension. Though every effort has been made to be accurate, please inform the author of any mistakes or omissions at kurt.jones@colostate.edu. The information given herein is supplied by CSU Extension with the understanding that no endorsement of named products is intended, nor is discrimination or criticism implied of products mentioned or not mentioned. To simplify technical terminology, or for the purpose of information, trade names of products and equipment occasionally will be used.