Classification | Small | Intermediate | Large | |
AEC calculation basis | Calculated net renewable thermal output | Calculated net renewable thermal based on indirect metering | Calculated net renewable thermal output based on direct metering of fuel input | Metered net renewable thermal output |
Solar thermal: evacuated tube and flat plate solar hot water | Collector surface area less than or equal to 660 sq ft | Collector surface area between 660 and 4,000 sq ft | - | Collector surface area greater than or equal to 4,000 sq ft |
Solar thermal: solar hot air | - | Collector surface area less than or equal to 10,000 sq ft | - | Collector surface area greater than 10,000 sq ft |
Solar sludge dryer | - | - | - | All |
Eligible Biomass Fuel | - | - | Capacity less than or equal to 1,000,000 Btu per hour | Capacity greater than 1,000,000 Btu per hour |
Compost heat exchange system | - | - | - | All |
Air source heat pump: electric motor or engine driven | Output capacity less than or equal to 134,000 Btu per hour | - | Output capacity between 134,000 and 1,000,000 Btu per hour | Output capacity greater than or equal to 1,000,000 Btu per hour |
Ground source heat pump | Output capacity less than or equal to 134,000 Btu per hour | - | Output capacity between 134,000 and 1,000,000 Btu per hour | Output capacity greater than or equal to 1,000,000 Btu per hour |
Deep geothermal | - | - | - | All |
Small Generation Units shall have the option to be classified as either intermediate or large Generation Units if they wish to forgo pre-minting and instead meter their Useful Thermal Energy as required by the Guideline on Metering and Calculating the Useful Thermal Output of Eligible Renewable Thermal Generation Units - Part 2 (Metering for Intermediate and Large Generation Units). Intermediate Generation Units shall also have the option to be classified as large Generation Units if they wish to meter their Useful Thermal Energy as required by the Guideline on Metering and Calculating the Useful Thermal Output of Eligible Renewable Thermal Generation Units - Part 2 (Metering for Intermediate and Large Generation Units). Generation Units which opt to change their size classification must notify the Department in their Statement of Qualification Application and must remain their chosen size classification for the duration of their qualification period.
For new construction, the small air source heat pump Renewable Thermal Generation Unit must supply 100% of the building's total annual heating and cannot have any supplemental, non-renewable heating sources. In retrofit construction or existing buildings, all small air source heat pump Renewable Thermal Generation Units that do not meet the above requirement must be used as the primary source of heat, supply at least 90% of the total annual heating, be integrated to a heating distribution system, capable of distributing produced heat to all conditioned areas of the building, and have a heat-rate capacity at five degrees Fahrenheit that is at least 50% of the nameplate capacity of the existing heating source equipment.
Small Ground Source Heat Pump System Type | Cooling Energy Efficiency Ratio | Heating Coefficient of Performance |
Closed loop water to air | 17.1 | 3.6 |
Open loop water to air | 21.1 | 4.1 |
Closed loop water to water | 16.1 | 3.1 |
Open loop water to water | 20.1 | 3.5 |
Fuel Quality Specifications | Pellets | Chips |
Calorific value | Greater than 8,000 Btu per pound | Greater than or equal to 5,500 Btu per pound |
Moisture | Less than or equal to 8% | Less than or equal to 35% |
Ash content by weight | Less than or equal to 1% | Less than or equal to 1.5% |
Chip size (percent retained by a 1/2 inch mesh screen) | Not applicable | 75% or adhere to manufacturer's protocol |
Chlorides | Less than or equal to 300 parts per million | Not applicable |
Performance Requirement | Pellets | Chips |
Thermal efficiency at nominal output | Greater than or equal to 85% Higher Heating Value | Greater than or equal to 75% Higher Heating Value or Greater than or equal to 80% Lower Heating Value if EN303-5 is used to verify particulate emissions |
Start up | Adhere to manufacturer's ignition protocol | |
Modulation/shut off | The system must automatically modulate to lower output and/or turn itself off when the heating load decreases or is satisfied | |
Pressurized portion of the system | Compliant with 522 CMR 4.00: Heating Boilers and Other Heat Storage Sources | |
Thermal storage | Required, unless an exception is issued by the Department | |
Fuel storage | The system must have covered bulk storage | |
Feedstock conveyance | The system must be automatically fed from feedstock storage to the furnace or boiler |
Lead Boiler System Size (Heat Input) | Thermal Storage Required |
Less than 80,000 Btu per hour | 80 gallons |
Between 80,000 Btu per hour and 119,000 Btu per hour | one gallon per 1,000 Btu per hour |
Between 119,000 Btu per hour and 1,000,000 Btu per hour | 119 gallons |
Greater than 1,000,000 Btu per hour | two gallons per 1,000 Btu per hour |
An Owner or Operator of a Generation Unit may apply for an exception from the requirements in 225 CMR 16.05(4)(g)4. if it can demonstrate to the Department that an inclusion of thermal storage would deteriorate the efficiency or air emissions performance of the Generation Unit, or the system can maintain efficiency and air emission performance at low capacity without thermal storage.
A boiler or furnace of less than 3,000,000 Btu per hour rated heat input must meet the applicable emission limits below: | ||
Pollutant | Pellets/liquid biofuels/biogas | Chips |
Particulate Matter | No more than 0.08 lb PM 2.5 per 1,000,000 Btu input or No more than 0.03 lb PM2.5 per 1,000,000 Btu input at sensitive populations | No more than 0.10 lb PM2.5 per 1,000,000 Btu input or No more than 0.05 lbs total PM per 1,000,000 Btu input if EN303-5 is used to verify emissions or No more than 0.03 lb PM2.5 per 1,000,000 Btu input at sensitive populations |
Carbon monoxide | No more than 270 parts per million at 7% oxygen | No more than 270 parts per million at 7% oxygen |
A boiler or furnace of greater than or equal to 3,000,000 Btu per hour rated heat input: | ||
Particulate matter, carbon monoxide, and other relevant criteria pollutants | MassDEP plan approval required, pursuant to 310 CMR 7.02(5). |
For the purpose of 225 CMR 16.05(4)(f)5., sensitive populations include schools, hospitals, nursing homes, or additional facilities determined by the Department.
The Department will review the Department's Guideline on Biomass, Biogas, andBiofuels for Eligible Renewable Thermal Generation Units every two years in consultation with the MassDEP and DCR and update the Guideline where appropriate.
The Department will assess the impact of biomass heating on the region's forests in 2018 and 2020, as well as every five years thereafter in coordination with the Forest Impact Assessment under the Renewable Portfolio Standard Class I, as prescribed in 225 CMR 14.06(8)(b) 2., and make changes as necessary. The Department will report annually on the aggregate woody biomass fuel
Class | Fuel Being Displaced | Minimum Combined Percentage of Forest Derived Residues, Non-forest Derived Residues, and Forest Salvage |
Class I | Natural gas, electric resistance, propane, fuel oil #6, fuel oil #2 | 55% |
Class II | Electric resistance, propane, fuel oil #6, fuel oil #2 | 50% |
Class III | Fuel oil #6, fuel oil #2 | 35% |
Upon qualification, Generation Units will be notified by the Department which fuel class they must purchase when sourcing fuel from a supplier on the Department's Biomass Suppliers List. Any Generation Unit that desires to purchase fuel from a supplier not on the Department's Biomass Suppliers List may request approval from the Department and shall be required to provide additional information. Generation Units displacing an existing biomass system shall have their fuel class determined by the Department.
225 CMR, § 16.05