Remote - Winter 2012 - (Page 10)

Feature Article When Does Solar Make Sense for Remote Sites? Bruce Gould, Director of Sales, Industrial Power Group SunWize Technologies Use of solar power (photovoltaics or solar electricity) for terrestrial applications emerged in the mid 1970’s. Inspired by the first oil embargo, solar was initially deployed for remote homes and for small industrial applications, ironically in the oil & gas industry. Industrial users of solar quickly learned that it was an effective technology for powering small devices with modest energy consumption in remote locations, where access to commercial power or the operation of a fossil-fueled generator was prohibitively expensive. Since its introduction, solar has exploded as a power source, with literally hundreds of thousands of systems deployed in North America and perhaps millions of systems worldwide. With that many systems under deployment it is clear that solar is an extremely effective technology for addressing many applications spanning numerous industry segments. Therefore, it is incumbent upon the system designer/ project planner to consider solar as a possible power strategy. When does solar make sense? Why has it proven to be so effective for some applications, but not for others? What should the system designer examine when faced with a decision about the provision of power to their site? This article presents six questions and points of consideration. If you can answer “yes” to these questions, it is likely you have an excellent application for a standalone solar system. ancillary items (controller, breakers, terminal blocks, battery/control enclosure, interconnect wiring, user’s manual, pre-assembly and packing) might cost $1,100. This system would typically mount on a single pole or mast and would be installed in one to two hours. It quickly becomes clear that any other power alternative, such as extension of the utility grid or the operation of a prime-power engine generator, would cost significantly more than this, making solar the clear economic choice. Consider also how reliable a welldesigned solar system is, with no moving parts and little to no required maintenance (see question 4), and solar once again becomes the obvious choice. Alternatively, consider a load of 1,000 watts, also operating in south Texas. This would require a solar system with an array of roughly 12,000 watts and a battery bank of over 12,000 amp-hours of capacity. Such a system would be ground-mounted (not polemounted) and would span about 70 ft. of width by 14 ft. of depth and could cost $150,000. At that level it is possible and even likely that extension of the grid or operation of a generator set would be a better economic solution. For larger loads like the 1,000-watt example above, we can consider solar in a hybrid combination with an on-demand generator, such as a diesel or propane generator set. Doing so expands your load range up to as much as 2000 watts continuous, which is shown in Figure 1 with standalone solar serving loads up to 12 kWh/day (500 watts), solar hybrids up to 50 kWh/day (2,000 watts) and stand-alone on-demand generators for loads above 50 kWh/day. There is no technical barrier to the use of solar for any load. Solar is an energy technology that produces whatever level of energy is required on a daily basis to sustain any piece of equipment. However, since the size of the solar array (the total collection of solar modules required) and the battery bank is directly proportional to the daily load requirement, at a certain size solar becomes very large and may not be logistically or economically feasible. Solar systems make great economic sense when powering loads of 500 watts continuous demand or less (12 kWh/day). Let’s consider an example, a gas flow meter on a remote section of gas pipeline in south Texas, with a load demand of 3 watts Figure 1. continuous at 12 volts DC. The result would be a complete solar power supply centered around a single 40 watt solar module and a single 37 amp-hour, 12 Vdc battery (representing five days of reserve autonomy). A system packaged with these components plus all 10 www.RemoteMagazine.com 1) Is Your Load (the Equipment to be Powered) Less Than 500 Watts Continuous (12 kWh/day)? Solar is an excellent remote-site technology since it is co-located with the load equipment. It does not require long-distance trenching of power lines. The power goes where the load goes, making solar an ideal distributed power supply. Conversely, extension of utility power, while possible, can be very expensive (we have been given rough estimates of $20,000 per mile) and the optimum route for the extension is often blocked by right-of-way issues. Further, since the utility is at a high AC transmission voltage, you will likely need a step-down transformer and a DC power supply if the load being powered requires a DC voltage (see question #3). Operating a prime power engine is also possible as a solar alternative, and can be more cost effective than extending the utility grid. However, rotating engines require regular refueling and maintenance. When considering that option, it is important to assess those ongoing operating and maintenance (O&M) costs as they are a real factor in your longer-term cost of ownership. 2) Is Your Load in a Remote Location with Limited, or No Access to Commercial (Grid) Power? http://www.RemoteMagazine.com

Table of Contents for the Digital Edition of Remote - Winter 2012

Remote - Winter 2012
Editor's Choice
Automated Monitoring Out at the Network Edge
What’s in Your Radio Communication Tackle Box?
When Does Solar Make Sense for Remote Sites?
Utility Networks in Transition
TV White-Space Technology Makes Broadband Affordable for Remote Locations
Challenges of Remote Management over Satellite
SCADA Market: Charting Strong Growth Amidst Industry Speculation
SCADA
Networking
Security
Oniste Power
Environmental Monitoring
Industry News

Remote - Winter 2012