Technical PaperPower Choices for Remote Site Prime &
Backup Power Systems
RedHawk Energy Systems, LLC 10340 Palmer Rd., S.W.
Pataskala, OH 43062
ph: 740-964-4000 www.redhawkenergy.net
Purpose: There are several choices of technologies available related to power systems for remote site prime and backup applications. This paper is focused on those power systems that are appropriate for applications in the range of 5 to 5000 watts.
Choices:Among the available choices for locally generating electrical power (AC and/or DC) when a utility connection is not available and/or too expensive:
While all of these choices can work in a given application, the most appropriate choice requires an analysis of the specific application needs, the local environmental conditions, and the operating conditions (including desired maintenance intervals) involved.
Photovoltaic (Solar) Power SystemsReliable, proven source of DC power by converting sunlight directly into electricity.
Wind Turbines Durable source of DC power by capturing the energy of moving air and converting it into electricity.
Fuel Cells Solid state DC generator that converts chemical energy into electricity.
Thermoelectric Generators (TEGs) Reliable source of DC power by converting heat directly into electricity.
Hybrid Power SystemsCombining power generation systems to increase overall system reliability.
Power Choices for Remote Site Prime & Backup Power Systems
Visit www.redhawkenergy.net/solar.html for more info
RHTechPaperPwrCh
Photovoltaic (Solar) Power Systems
Application Considerations:
PV Advantages:
PV Disadvantages:
PV (solar) power systems provide a reliable, proven source of DC power by converting sunlight directly into electricity. PV modules require very little maintenance with the occasional cleaning of modules, check of elec-trical connections, check of system regulators and check of battery storage systems. PV systems operate on “sunlight” and therefore don’t incur any ongoing fuel costs or requirements. Most PV modules are designed and rated to provide reliable performance and life for 20+ years. Nominal PV module voltages of 12 and 24 volts can be scaled in a series and/or parallel configurations to accommodate and extended range of system operating voltages and power ratings. Because PV modules are DC power sources, the use of inverters and/or converters can be used to provide mult-voltage DC or AC output.
PV systems are intermittent generators of power. Loads requiring power at times other than when the sun is shining require an energy storage sys-tem (batteries). Batteries (pictured right) provide an energy storage buffer and are used to accommodate loads that need to be powered through the night and over extended periods of inclement weather. Proper mounting structures are required to hold the individual PV modules in a system, allow integrated system wiring, and enable proper alignment and module tilt to optimize energy capture. PV systems are effective in most places with unobstructed access to sunlight. Specific location factors will impact the structure design and should be taken into consideration such as: wind loading, expandability, maintenance, and exposure to theft/vandalism.
“PV systems are effective in most places with unobstructed access to sunlight”
• Proven Source of DC Power• No Waste Byproducts/Emissions• No Ongoing Fuel Costs
• Require Direct Exposure to Sunlight
• Larger Footprint Compared to Other Power Solutions Due to Panel Inefficiencies
• Shading From Trees, Hills & Mountains Can Present Issues
• Susceptible to Vandalism & Theft
• Low Maintenance • “Green” Energy Producer• 20+ Years Life (Panels)
Solar (PV)
Power Choices for Remote Site Prime & Backup Power Systems
RHTechPaperPwrCh
Wind Turbines
Application Considerations:
Wind Turbine Advantages:
Wind Turbine Disadvantages:
Wind Turbines capture the energy of moving air and convert it into electricity. A wind turbine typically consists of a rotor, electric genera-tor, and a control system. The rotor, which looks much like an airplane propellor in most cases, is turned by the wind. The rotor is connected to a shaft which either directly or through a drive mechanism turns the armature of the generator thereby creating electricity. The control system manages the interface to the load. Because of the speed variability of the wind, wind turbines have a DC power output.
Most wind turbines do not begin to generate any useful power until wind speeds reach 7-10mph and do not generate rated power until wind speeds reach the mid 20mph range. Like solar systems, if loads need a continu-ous source of power, an energy storage system (batteries) needs to be used. Due to the much more intermittent nature of wind compared to solar, the necessary energy storage system (batteries) would need to be larger than that of solar. Often, solar and wind technologies (remote applications) compliment each other in a hybrid power solution.
“Wind Turbines are best suited for areas which average windspeeds of 12mph or greater“
Visit www.redhawkenergy.net/wind.html for more info
• “Green” Energy Producer• Non-Polluting • No Ongoing Fuel Costs
• Useful Power Isn’t Generated Until Speeds Reach 7-10mph• Rated Power Isn’t Generated Until Speeds Reach Mid 20mph Range• Noisy Operation• May Have Negative Impact on Wildlife (Birds)• Requires Regular Maintenance
Wind
Power Choices for Remote Site Prime & Backup Power Systems
RHTechPaperPwrCh
Solid Oxide Fuel CellsA Solid Oxide Fuel Cell (SOFC) is an electrochemical reaction device that converts fuel and air into electricity. These fuel cells consist of two electrodes (the anode and cathode) that are separated by an electrolyte. Fuel is added to the anode side of the fuel cell and air is added to the cathode. Electricity is produced when the fuel and oxygen from the air combine forming water. One of the key differences between SOFC and most fuel cell technologies is the process in which electricity is produced. While most fuel cells generate electricity by moving fuel through electro-lyte, a SOFC moves oxygen from the air through electrolyte. The result is a system that is able to process conventional fuel such as propane and natural gas.
Powered by commercially available and low cost propane or natural gas, Solid Oxide Fuel Cells have the ability to sit in a standby mode for months at a time monitoring battery voltage and are then able to automatically start when the primary power source is lost ensuring critical applications have 100% reliable power or to operate as a primary power generator in remote applications. When compared to other fuel cell solutions, a SOFC offers a much broader environmental operating and storage enve-lope. Because a SOFC utlilizes a ceramic electrolyte they are not susceptible to freezing and thawing cycles that are a common problem for fuel cells that use a hydrated polymer membrane such as Proton Exchange Membrane (PEM) fuel cells. A SOFC can operate in very cold climates (-40°C to 50°C), whereas other fuel cells may require continuous electrical energy input or the unnecessary consump-tion of fuel to prevent freezing. Temperature compensated charging algorithms provide accurate and optimized battery state of charge management regardless of changes in ambient conditions which minimizes the # of charge cycles to maximize fuel cell efficiency and extend the functional life of the backup batteries and consume less fuel.
Visit www.redhawkenergy.net/ultamifuelcells.html for more info
Application Considerations:
“SOFC” Advantages: “SOFC” Disadvantages:
• Reliable Starting After Extended Storage• Runs on Readily Available & Low Cost Propane or Natural Gas• Wide Operating Range (-40°C to 50°C)• Low Maintenance• Very Low Emissions (traces of carbon dioxide & water vapor)• Clean“Eco-Friendly” Energy Producer• Quiet Operation
• Requires Local Fuel Source for Operation• Power Isn’t Instantaneous (approx 30 min startup)• Not Well Suited for 24/7 Prime Power Applications• Needs Air/Ventilation for Operation (can’t be confined)• Larger Upfront $ than Diesel/Gas Generators
Fuel Cells
Power Choices for Remote Site Prime & Backup Power Systems
RHTechPaperPwrCh
Proton Exchange Membrane Fuel CellsA Proton Exchange Membrane (PEM) Fuel Cell is an electrochemical conversion device. A PEM fuel cell is comprised of two adjacent chambers - the anode side and the cathode side - separated by a membrane. Hydrogen gas from the fuel processor enters the anode side where the atoms release their electrons when reacting with a platinum catalyst on the membrane. The anode chamber then becomes flooded with free electrons and with hydrogen protons (hydrogen atoms stripped of their electrons). The positively charged hydrogen protons pass through the membrane into the cathode side of the fuel cell. The electrons exit the anode side and flow into an external electrical circuit. After running through the circuit, the electrons re-enter the fuel cell on the cathode side, completing the electrical path. On the cathode side, the hydrogen protons that passed through the membrane combine with the free electrons and with oxygen molecules to produce pure water and heat.
Like engine generators, fuel cells require a local fuel source - with the amount of operating time dependent on local fuel storage capability and refueling intervals. A fuel cell operates best at load conditions near its rating, as its not well suited for very light loading. Current PEM designs are best suited for “backup” power applications rather than continuous prime power applications. PEM design fuel cell stacks have a shorter life expectancy as compared to other technologies discussed in this paper. While PEM design fuel cells expected operation lasts several thousand hours and is quite adequate for years of standby and/or backup service, a 24/7 operation would require the fuel cell stack to be changed out every few years which would get $ expensive. PEM fuel cells do not provide instantaneous power and different designs have vary-ing start-up times that range from a few seconds to several minutes. Some designs will incorporate a small battery bank or ultra capacitor to bridge the startup time.
Visit www.redhawkenergy.net/bpsfuelcells.html for more info
Application Considerations:
“PEM” Advantages: “PEM” Disadvantages:
• Extended Run Backup Power• Onsite & On-Demand Hydrogen Production• Low Maintenance• Very Low Emissions• Clean“Eco-Friendly” Energy Producer• Quiet Operation
• Requires Local Fuel Source for Operation• Power Isn’t Instantaneous (approx 30 min startup)• Not Well Suited for 24/7 Prime Power Applications• Hydrating of Stack is Required Periodically• Larger Upfront $ than Diesel/Gas Generators
Fuel Cells
Power Choices for Remote Site Prime & Backup Power Systems
RHTechPaperPwrCh
Thermoelectric Generators Thermoelectric Generators (TEG) are extremely reliable, low main-tenance, long-life generators which provide continuous DC power by converting heat directly into electricity. As heat moves from a gas burner through a thermoelectric module, it causes an electrical current to flow. A hermetically sealed thermoelectric module, called a thermopile contains an array of semiconductor elements. When heat from a burner is applied to one side of the thermopile and the other side is kept cool via cooling fins, the temperature difference across the thermopile creates steady DC electricity with no moving parts. The technology dates back to the 1960s and has been deployed around the world and in space.
TEGs typically range in output size from 15 to 550 watts and can be combined to power applications requiring up to 5,000 watts. They are designed to run on either propane, butane or natural gas. Outputs can provided to match virtually any DC or AC voltage requirement. TEGs are designed for continuous operation; which means that expensive battery systems, which need maintenance and periodic replacement, are not a re-quired component of this power system. If batteries are used to cover high peak loads, TEGs operate in float charge mode which assures long battery life. TEGs are well suited for both prime and standby applications, though like a fuel cell, they do not instantly produce full power upon startup. Requirements for operation of TEGs include: a mounting stand for the generator (to keep it from being inundated with water or snow), a local fuel supply (propane, butane or natural gas), and electrical connections to the load. A small battery bank may be integrated to cover peak loads, bridge the startup time or to provide emergency backup.
Application Considerations:
TEG Advantages TEG Disadvantages
• Solid-State Design Ensures Trouble-Free Operation & Reliability• Well Suited for Both Prime & Standby Applications• Low Maintenance• Competitive Capital & Operating Costs• Thermopile (20+ year) Life• Operation in Any Climate (hot, cold, wet, dry)• Small Footprint• Batteries are Not Required Component
• Requires Local Fuel Source for Operation• Power Isn’t Instantaneous Upon Startup• Low Operating Efficiency • Not Suited for Applications Higher than 5kW• Larger Upfront $ than Diesel/Gas Generators
Visit www.redhawkenergy.net/teg.html for more info
TEGs
Power Choices for Remote Site Prime & Backup Power Systems
RHTechPaperPwrCh
Hybrid Power SystemsWith Hybrid Power Systems different power generation and storage units are combined to meet the energy/power demands of the application. Hybrid systems are often utilized in cases where just one power solution isn’t able to provide the adequate power required to power the load. When two systems are combined they compliment each other.
Solar & Wind Hybrid Power Systems (pictured top right) are a popular choice for applications that experience varying weather conditions. When the sun is shining the solar array is powering the load and at night and on cloudy windy days the wind turbine is picking up the slack. An energy storage system (batteries) is used to store the power generated and to pro-vide continuous power to the load.
Solar & Fuel Cell Hybrid Power Systems (pictured right) are ideal for ap-plications that experience unfavorable weather conditions and/or peak load conditions. The solar array converts sunlight into electricity and the solar controller charges the energy storage system (batteries). If the batteries are fully charged and are above a predetermined threshold voltage, the fuel cell is idle. When the batteries dip below the lower threshold, the fuel cell will automatically turn on. After a startup period (25-30 min), the fuel cell will begin charging the batteries and powering the load.
Solar & TEG Hybrid Power Systems combine the economics of Solar with the reliability of a TEG. The solar array generates power during times of abundant sunshine, while the TEG provides power during times of insuf-ficient solar radiation, periods of inclement weather and peak load condi-tions. An energy storage system (batteries), though not a requirement for TEGs, is often used to store the energy generated and cover high peak loads.
Solar & Generator Hybrid Power Systems are often used in applications with high power requirements. The solar array provides power during times of abundant sunshine while the generator powers up during periods of limited sunshine and/or to cover peak load conditions. An advantage of this type of system is that the solar array provides base load support and helps to reduce the refueling needs of the generator.
Hybrid System Advantages
Solar (PV) & Wind
Solar (PV) & Fuel Cells
Solar (PV) & Thermoelectric Generators
Solar (PV) & Extended Run Generators
• Increased Reliability• Availability & Flexibility• Utility-Grade Power Potential • Longer Equipment Life
Visit www.redhawkenergy.net/hybridsystems.html for more info
Hybrids
Power Choices for Remote Site Prime & Backup Power Systems
RedHawk Energy Systems, LLC 10340 Palmer Rd., S.W.
Pataskala, OH 43062
ph: 740-964-4000 www.redhawkenergy.net
RHTechPaperPwrCh
Scan QR Code
About Us
Our History: RedHawk Energy Systems, LLC was officially formed in 2004 and is a manufacturing and value-added subsidiary of the Arthur N. Ulrich Company. RedHawk specializes in the design, engineering, fabrication and installation of alternative energy systems and battery accessories for critical remote site, utility grid-tie and backup power applications. Since the early 1980’s, the Arthur N. Ulrich Company has designed and deployed alternative energy systems ranging from a few watts to several kilowatts for hundreds of applications throughout North America.
