As energy costs continue to rise, knowledge of energy efficient technologies and best practices are becoming more valuable. While these practices have slowly gained acceptance within the water and wastewater industries, increasingly strained budgets coupled with aging infrastructure make energy efficiency a feasible option to save money. Through desire and innovation, our staff has kept the Authority on the cutting edge of energy efficient technologies. As eluded to in the history page of this website the Authority, for the most part, pioneered microturbine technology utilizing anaerobic digester off-gases. In fact, its pilot program was the first of its kind to be successful in North America. That 30 KW digester gas-fired microturbine generator provided the Authority with yet another opportunity to apply current technology with exceptional pay back that proved to further reduce its increasing energy demands.
Upon completion of the Anaerobic Digestion Complex Refurbishment and Upgrade Project in the spring of 2007, the production of digester gases not only increased significantly, but their rate of generation was more stable and easier to predict. During 2008 it became apparent that the Authority should move from the microturbine Pilot Scale generation of electricity to Full Scale, as such a Co-Generation Project Technology Evaluation was undertaken.
Our evaluation focused on microturbine and internal combustion engine technologies. Equipment manufacturers of the above-referenced technologies were provided with current operating data which defined annual digester gas production and digester gas properties. They were requested to select the size and quantity of their equipment with the ultimate goal of providing the maximum annual electrical energy and heat production as a function of available digester gas. Other pertinent data required to be provided by the equipment manufacturers included expected emission rates, the capital cost of equipment including gas conditioning systems, noise, delivery time, and description of proposed factory protection plan and associated cost of the plan.
Once all information was received from the equipment manufacturers, staff and consultants proceeded to conduct life cycle analyses for each of the responses received in the effort to identify the most cost-effective technology for the Authority’s co-generation project. The life cycle analyses considered equipment capital cost, potential rebate amount, annual electrical and natural gas energy savings, and cost of the factory protection plan. The present value of all costs, rebate amount and energy savings was calculated over a nine 9 year timeframe (duration of a standard factory protection plan) at an interest rate of 3%. The technology has the highest net present value was deemed to be the most cost-effective technology. Non-cost factors were also considered in the overall technical evaluation which included the amount of excess gas required to be flared via the waste gas burners, emission rates, and noise. All pertinent data had been compiled and summarized in an “Evaluation Summary- Microturbines verses Internal Combustion Engines”.
As a result of that analysis, the internal combustion engines proposed by Senergie (2 units at 140 kW each) exhibited the highest present value and therefore were deemed to be the most cost-effective technology for the Authority’s co-generation project. In addition, the proposed combined heat and power co-generation system proposed by Senergie utilizes all available digester gas for the production of electrical and heat energy and therefore will not require flaring of excess digester gas, satisfies the allowable emission rates, and easily met established noise criteria of 70dB (A) at a distance of 1 meter (3.3 feet) from the equipment. In fact at the assumed property line of the Authority (a distance of 25 feet from the co-generation equipment), the noise level at this distance reduces to 52 dB(A) which is equivalent to the noise produced by a window air conditioner unit.
Based upon the recommendation of staff the Authority once again decided to move forward with a significant capital investment in an effort to reduce its dependency on third-party energy providers, reduce its carbon footprint, and moreover insulate its User-base form upward spiraling and out of Authority control increases in energy cost.
By the spring of 2010, the project had been designed, publically bid, constructed. The system underwent start-up operations during February and was officially placed into service on March 1, 2010. The table below clearly demonstrates the effectiveness of the project.
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The Authority remains firmly committed to its energy conservation program, and has put in place the following Best Management Practices to ensure it’s continued efforts into the future:
* Benchmark it’s energy consumption to that of other similar facilities.
*Performed continued assessments to identify best practices to save energy.
* Established a capital improvement program to generate funds to implement energy-efficiency projects.
* Appointed an energy advocate among facility staff to champion energy-efficiency projects.
* Instituted a program to continuously monitor, review and assess energy consumption on a monthly and yearly basis.
* Developed and maintained communications with management to increase awareness of the value of energy management.