Brattleboro Thermal Utility/BTU (see www.brattleborothermalutility.org) recently commissioned a feasibility study on the possibilities for district energy (heating a whole section of town via just one energy plant) in Brattleboro.

The following was written by Dan Ingold, a consultant from Powersmith Farm in Guilford. Dan has been working for BTU as its "owner's representative" during the study.

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Report to Brattleboro Select Board on the
FEASIBILITY STUDY OF BIOMASS FUELED COMBINED HEAT AND POWER FACILITIES AND ASSOCIATED DISTRICT ENERGY INFRASTRUCTURE IN BRATTLEBORO, VERMONT

Background:
The Town of Brattleboro received a $20,000 Clean Energy Development Fund grant to carry out this feasibility study. The Town also appropriated $5,000 of its own funds. The Town has subcontracted responsibility for this study to Brattleboro Thermal Utility (BTU) a non-profit group whose board members are all local.

BTU chose Waldron Engineering and Construction of Exeter, NH (alliance with NRG Thermal) for the Study, with additional support from the Biomass Energy Resource Center (BERC) of Montpelier, Vermont.

The study’s prime purpose was to review the existing heating needs within Brattleboro and construct an economic dynamic model to examine and determine feasible options for ownership, structure and size of a project.

The study began in early summer, and the draft of the final report has been submitted.

Concept:
The basic premise is to use wood fuel for producing steam at high pressure- this steam is then used to spin a turbine to produce electricity, and the resulting lower pressure steam is then distributed via underground insulated pipes to one ore more Districts of the community as steam or hot water. (This Cogeneration approach is a much more efficient use of fuel than plants that generate electricity only.) Each building customer would use a thermal exchanger to heat their space, and pay according to amount of heat used. It is assumed that between 1.6 million and 2 million square feet of buildings within Brattleboro would utilize the system.

One of the advantages of District Heating and Cogeneration is that there are various business units that can be the basis for local jobs and enterprises. These include:

• Fuel Supply- for timber & forest managers, loggers, chippers and trucking.
• Thermal & Electric Commodity Production- for operating the boiler plant, revenues are from electricity and hot water sales
• Thermal Commodity Distribution- for managing the underground piping and use quantities. This could be similar to Algiers Fire District, which manages the sewer lines in Algiers, Guilford and then uses the Brattleboro treatment plant.
• Thermal Point of Use- plumbing and HVAC work will be needed to set up and maintain the thermal exchange systems.

This District Energy project would provide more local jobs and reduce energy dollars going out of the community.

Cogeneration Plant Options Considered:
The BTU Board and Waldron worked together to determine and examine feasible options- and they are:

1. Thermal Leading- All biomass fuel
The cogeneration plant is sized for peak heating loads, hot water is the primary factor and the electric production is a by-product (1.6 megawatts). This is the most energy “conversion” efficient option, but because the design and installation of equipment is sized for “peak loads” the capital cost is extremely high, and most of the time the equipment that allows you to meet the peak loads is sitting idle. This cogeneration plant would use 29,000 tons of woody biomass per year (1 truckload is 20-22 tons).

2. Electric Leading- all biomass fuel
The cogeneration plant is sized to maximize electric production (15 megawatts), but there is enough by-product steam to serve the heating needs of customers. In the summer most of the by-product steam is not needed, so is “wasted inventory” and must be cooled. This cogeneration plant uses 240,000 tons of woody biomass per year.

3. Thermal Leading “hybrid” - mostly biomass fuel (90%), some oil (10%)
This cogeneration plant uses biomass fueled boilers for up to 75% of peak load, with oil fueled boilers available for emergency and to cover heavy thermal load days. The initial estimate is that the woody biomass fueled boilers would provide 90% of the needs over the course of a year. It would use 32,000 tons of woody biomass. The electric production is 1.9 megawatts. The advantage of this approach is that the capital cost for the biomass fueled system is reduced, because less is needed. Biomass fueled boilers with fuel handling systems are much more expensive than oil boilers with fuel tanks. The report from Waldron shows this configuration as the most pragmatic and with the best chance of economic success. The draft feasibility study shows that for the ‘Hybrid” system the estimated costs are:

• Central cogeneration plant: $ 18,900,000
• Hot Water Distribution: $ 3,525,000
• Individual (total) interconnection: $ 1,750,000

This system should provide heat for 2,000,000 sq ft (equivalent of 800 homes) at a cost less than current oil based heat. The electric power is enough for over a thousand homes.

Additional Options: Multi Node Approach
The primary concept may be a central cogeneration plant, but there is also the opportunity to include smaller individual thermal production plants on the hot water pipeline. As an example a manufacturing facility or apartment complex may want to have its own system (like the Hooker Dunham Building) but also be interconnected to the district thermal piping. They then have “back up” and they can also feed excess capacity into the district thermal piping.


Cogeneration Plant:
The Brattleboro High School/Middle School/Vo-Tech Center is biomass fueled (but thermal only-no cogeneration) and heated with a boiler with a peak capacity of 10 million BTU’s per hour. It uses up to 1,600 tons of woody biomass per year. The cogeneration plants being considered have boilers that range in size from 56 million BTU’s per hour (Thermal Leading) up to 146 million Btu’s per hour (Electric Leading) and would need 29,000 to 240,000 tons per year of woody biomass fuel.


Customer Interconnect:
A heat exchanger would be installed within each distribution point, so that they are “isolated” from the central distribution fluid.


To help ensure the ability for customers to interconnect into the district heating system, a revolving loan fund could be established using grants to finance the heat exchanger and associated piping.

Next Steps:
The logical steps will be review of the Feasibility Study, and then determine if there is a desire to move forward. Before further engineering studies are initiated, decisions on the ownership structure of the District Energy System and its components will be needed- as an example, will the central heat and power plant be privately owned and operated and sell the hot water to a municipal or non-profit entity that then distributes and sells to community customers?

After the town and community decides what form and components of the District Energy System are in the best interest of Brattleboro, then engineering studies will be needed for the distribution work, and central plant site options will be investigated.

To fund future phases BTU will need to apply for additional grant funds at the state and federal levels, and potentially seek private partners as well.

Potential Impacts “Vermont Energy Act of 2009”
This new endeavor by Vermont will have affect on the Brattleboro Community with the following components:

• improvements to residential and commercial-building standards;
• pilot downtown-community renewable-energy projects in Montpelier and Randolph (combined heat and power facilities)- note: if either of these Towns decides not to move forward, then Brattleboro could replace them in this pilot program which dictates funding grants for customer interconnections.
• clean energy assessment districts that would allow towns, cities, and incorporated villages to use municipal bonds to finance residential renewable-energy or energy-efficiency projects (this includes district energy projects); and
• limitations on the power of municipalities and deeds to prohibit residential installation of renewable-energy and energy-efficiency devices, such as solar panels and residential wind turbines