423 GVEA – Anderson Solar Thermal Heat & Ground Storage
Proposer: Golden Valley Electric Association
Benefit/Cost Ratio: Applicant 2.45 AEA 1.18 Maximum (Speculative) ISER NS: 2.78
ISER NS/GF: Recommend using the ISER NS analysis
GVEA proposes funding of a $101,500 feasibility and design study for a combined/hybrid solar-thermal collection and storage system with ground-source heat pumps in Anderson public buildings. Both borough and municipal buildings (primarily the Anderson school) are targeted for a renewable offset in both electrical and building heat of 50% (currently $156,000/yr).
There are three sets of technology involved. In order of current “state of technology” we have Solar Photovoltaic, Solar Heat, and Seasonal Thermal Energy Storage. The last of these is developing but still-experimental technology. It has never been tried in Alaska. Seasonal storage and discharge of energy is accomplished with the use of underground tanks or pits.
Seasonal Thermal Energy storage has about a 30-year history of pilot/experimental facilities through large scale plants. The concept has been proven, but significant advances are still necessary. Interior Alaska is promising for solar energy collection. GVEA has specific experience in design of a solar hot water collection system in Denali.
GVEA has obtained two estimates from appropriate candidates (PDC Engineering and ABS Alaskan) that yielded similar quotes for services, and will acquire additional PhD engineering consulting on some aspects of the project. It is a well considered and researched proposal indicative of work that can be finished ahead of schedule.
Contribution to Lower the Cost of Energy:
The project proposes a design for offsetting 50% of both electrical and heating needs of the candidate buildings, currently 366,630 kWh of electricity use and 5,911 mmbtu of building heat. The electric generation is offsetting GVEA petroleum-generated energy. The building heat is replacing fuel oil.
Applicant, in good faith, suggested capital costs of $500,000 as an example for discussion of construction costs, but the design is undetermined so it remains speculative. In the B/C analysis that figure is increased by $100,000 - the amount of the proposed feasibility and design project.
The literature points to two areas due diligence requires addressing in facilities of this type that are experimental. The best most recent published research indicates there have been significant advances yet no “state of the art” technology has emerged in seasonal thermal energy storage. Thermal losses in the majority of facilities are significantly greater than predicted. Failure of liners and deterioration of insulation remain significant problems. To account for these the useful life was reduced from 30 to 20 years. Thermal losses, repairs or any other loss in efficiency relative to design was incorporated by assuming 80% of design performance.
The ISER NS analysis assumed the performance outlined in the application with 3,500 mmBtu of heat offset and a 6 to 1 heat to electric performance. Also assumed an existing diesel heater efficiency of 80%. In the ISER NS scenario, electricity is considered a cost, not a produced benefit.
Seasonal Thermal Storage is developing technology and reliability is more questionable as compared with commonly used technology. The buildings and heating systems vary but are on the order of 30 years. Consideration of how this proposed system integrates within the long term capital planning of the school and other buildings will require co-ordination. But the proposal has fielded a strong team and the project is in a small area, and all parties are already cooperating fully.
The system will take time to stabilize, the variability of solar collection is still an issue. Because it is a feasibility and design study, these are the major concerns of the work itself. The proposal is already demonstrative of significant scoping and assessment work as well as competence in recent literature.
Data on operating and maintenance of GSHP for commercial buildings is hard to come by, but survey results show tremendous variation (e.g. $2 to $38 per sq ft reported as median vs. worst-case scenario).
Additional solar panels are possible, but the point of the study is to design for optimal sizing at the outset.
The solar collection component is of course sustainable. Storage of excess capacity reduces over-all nonrenewable resource use.
Potential Public Benefits
The primary potential benefit for this project is the first-time application of new, developing technology to Alaska, and potential advancement along several trouble areas in the field. Generally speaking the capital costs are still too high, and the thermal losses too large for Thermal Energy Store systems. Specific improvement in optimizing soil works, store construction, and materials (aging of liners and insulation) would be beneficial to the developing science.
The secondary benefits are offsets in electricity and building heat requirements for the parties bearing these costs. This is a mix between the local community and the State of Alaska since the funding for electricity and heat in these buildings comes from a combination of both.
-- December 21, 2009