Qualifying Solar Thermal in the APS

The eligibility criteria and requirements for qualifying a solar thermal system in the Alternative Portfolio Standard.

Eligibility Criteria

All Renewable Thermal Generation Units must:

  • Generate useful thermal energy using sunlight, biomass, biogas, biofuel or naturally occurring temperature differences in ground, air or water
  • Deliver a useful thermal load to a facility located in Massachusetts
  • Have an operation date January 15th 2015 or later

A solar thermal Renewable Thermal Generation Unit must use collectors, to transfer solar irradiation energy to a working fluid, as well as a pump or fan to actively circulate the air, water, or other working fluid through the collectors. All solar thermal collectors must also have a performance certification issued by the Solar Rating and Certification Corporation, International Association of Plumbing and Mechanical Officials, or other performance certification approved by the Department. Unglazed flat plate collectors for pool heating are not eligible to qualify as an APS Renewable Thermal Generation Unit.

To submit a Statement of Qualification application (SQA), please visit the APS Renewable Thermal Application Portal.

For more information on renewable thermal in the APS, please visit our APS Statement of Qualification webpage

Size Classification and Multipliers

The size classifications for solar thermal Generation Units are as follows:

Technology Small Intermediate Large
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 hot air  N/A Collector surface area less than or equal to 10,000 sq ft Collector surface area greater than 10,000 sq ft

The multipliers for solar thermal Generation Units are as follows: 

Technology Small Intermediate Large
Solar hot water systems used for domestic hot water 3 3 3
Solar hot water systems used for domestic hot water, space condition, or process loads 1 1 1
Solar hot air systems N/A 5

Small Solar Thermal Generation Units

AEC Calculation 

Small solar thermal Generation Units are eligible to receive 10 years of AECs upfront. After reviewing and approving the application for the Generation Unit, DOER will calculate the 10 year strip of AECs to be minted. The equation to calculate the annual number of AECs is as follows: 

If using OG-100

If using OG-300

Surface Orientation Factor 

The Surface Orientation Factor (SOF) of a system is used to adjust the predicted thermal yield (collector rating) due to a decrease in production efficiency based on the tilt and orientation of the system’s solar thermal collectors. The SOF used to calculate Useful Thermal Energy output for Small, solar thermal systems is based on Massachusetts geographic location. See figure below:

Pool Heating

Small systems with a useful thermal load that is dedicated to heating a pool are eligible so long as they do not use unglazed flat plate collectors. If the pool is located indoors the same methodology as a typical domestic hot water load should be used. If the pool is located outdoors the same methodology should be used, but with the OG-100 Category B rating, see above.

More information on this calculation can be found in the Guideline on Metering and Calculating the Useful Thermal Output for Renewable Thermal Generation Units – Part 1 (Calculations for Small and Intermediate Generation Units)

Application Requirements 

All small solar thermal Generation Units are required to submit the following in their Statement of Qualification Application:

  • Site and facility information
  • Contact information 
  • Equipment specifications 
  • Design Specifications 
  • NEPOOL GIS information 
  • AEC Service Agreement (not required) 

Intermediate and Large Solar Thermal Generation Units

AEC Calculation

Intermediate and large solar thermal Generation Units will receive AECs, based on their metered production, on a quarterly basis. Generation Unit owners should review the Guideline on Metering and Calculating the Useful Thermal Output for Renewable Thermal Generation Units – Part 2 (Metering for Intermediate and Large Generation Units) for information on metering requirements. 

Application Requirements 

All intermediate and large solar thermal Generation Units are required to submit the following in their Statement of Qualification Application:

  • Site and facility information
    • Site plan (attachment)
  • Contact information 
  • Equipment specifications 
    • Equipment arrangement drawing  (attachment)
    • Annotated product literature for all major equipment (attachment)
  • Design Specifications
    • Description of System Controls and Sequence of  Operations (attachment)
    • A process flow diagram (attachment)
    • A one line electrical diagram (attachment)
  • NEPOOL GIS information 
  • AEC Service Agreement (not required, attachment)
  • APS Renewable Thermal Performance Workbook (attachment)
  • Independent Verifier request form (attachment)
  • A metering plan including a list of meters (attachment)
    • Annotated product literature for each APS meter (attachment)
    • Annotated product literature for the Data Acquisition System (DAS) (attachment)
  • Certified Performance Data Construct (intermediate Generation Units only) (attachment)

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