The methodology for the study involved a detailed, multi-step process. Site visits were conducted to assess the existing systems and available space at each location. Surveying of land areas helped identify potential sites for geothermal wells, while a review of the original construction drawings helped pinpoint underground utilities that could affect well placement. The team used Energy Plus energy modeling software to simulate the HVAC and DHW loads for each building to use as inputs for LoopLink Pro software that was used to estimate the quantity and depth of geothermal wells required. Furthermore, a Basis of Design (BOD) was created to select appropriate equipment, including water-source heat pumps, circulating pumps, heat exchangers, and DHW storage tanks. Finally, interior building spaces were surveyed to determine if they had enough room for the new equipment and if the building entries could accommodate the necessary machinery.

Solutions

Based on the findings of the feasibility study, several solutions were proposed. Due to the limited available land at all sites, it was determined that vertical geothermal wells would be necessary for all buildings. The locations of wastewater outlet pipes were identified as optimal for implementing wastewater heat recovery systems, which require external holding tanks and heat pumps inside the buildings. This system appeared to be an effective and space-efficient solution for meeting the DHW needs of the buildings. The surveys also revealed that all basements had adequate space for the new geothermal and wastewater heat recovery equipment. Preliminary calculations showed that there was sufficient land to meet the DHW demands, but not enough to handle the HVAC energy load, suggesting that additional land may be needed for HVAC geothermal systems.

Electrical upgrades were also identified as a significant requirement. The existing electrical infrastructure was found to be inadequate for handling the additional electrical load that would come with the electrification of HVAC and DHW systems. A review of electrical drawings revealed that the building's service size and conductors were likely too small to support the new systems, meaning substantial upgrades would be necessary to accommodate the geothermal systems.

Results

The results of the study will serve as a blueprint for NYCHA's future efforts to implement similar geothermal and wastewater heat recovery solutions across its housing portfolio. The feasibility study found that many of the existing HVAC and DHW systems were nearing the end of their service lives, providing a prime opportunity to replace these outdated systems with geothermal technology. The detailed cost and life cycle analysis are still pending, but early indications suggest that geothermal DHW systems are feasible, while HVAC systems may require additional land that may not be available at all sites.

Conclusion

In conclusion, the feasibility study conducted by FSG highlighted several key takeaways. First, the limited land area at each site means that vertical geothermal wells are necessary for all locations. However, the available land is insufficient to support the geothermal wells needed to meet the HVAC energy demand. Wastewater heat recovery, on the other hand, offers a viable and space-efficient solution for meeting DHW energy needs. The energy in the wastewater stream was found to be adequate to meet the peak DHW load, without requiring significant land area. Additionally, the existing electrical infrastructure was found to be insufficient to handle the added load from electrification, necessitating significant upgrades. The study's findings provide NYCHA with the information necessary to move forward with a comprehensive electrification strategy that includes geothermal systems and wastewater heat recovery, ensuring a more sustainable and energy-efficient future for its public housing portfolio.