By Charles C. Copeland, PE, LEED AP
From the December 2019 Issue
With the growing need to reduce carbon emissions from communities and facilities, understanding the full range of renewable energy options is paramount. One often-overlooked option is geothermal ground source energy. A new screening tool, created for all New York City lots to assess this technology, provides a free resource that other cities and counties can modify to their own geology, land area, and energy sources. It’s a tool that can shed light that is valuable to facility executives as well.
Geothermal ground source energy is distinct from other geothermal energy in that it is derived not from a hot spring or other geological geyser. Instead, it uses the ground as a reservoir, normally with temperatures in the 50°F to 60°F range, as a relatively stable storage medium for a heat pump system to either retrieve or store energy as a source of heating and cooling. North America is the key market for geothermal heat pumps, according to the International Energy Agency’s Technology Collaboration Programme on Heat Pumping Technologies¹, due to increased demand for renewable energy sources. Stable markets in Europe include Sweden, France, Switzerland, and Germany.
New York City’s Geothermal Ground Source Screening Tool document was developed for that city’s Mayor’s Office of Sustainability and the Department of Design and Construction by consulting engineering firm Goldman Copeland, of which I am President. The tool is available online² and was recently honored by the American Council of Engineering Companies of New York.
Other jurisdictions can adapt the tool—to determine their own ground source potential—using relevant topographical data usually available through U.S. Geological Survey maps. That data requires review by a local geologist and an experienced geothermal engineer, but the process can be facilitated by adopting the New York City model approach. In New York City, the tool enables users to simply assess the feasibility of ground source heating and cooling for every lot in all five boroughs in the city—almost 900,000 lots. The tool is especially helpful there in assessing the potential of new building structures to make use of available ground source capacity.
Ground source energy is thermal energy stored in the subsurface ground. It can be accessed from any number of larger lot areas, of which most cities and counties have many, to provide efficient heating and cooling for nearby buildings. This can be evaluated on a lot-by-lot or district basis, but larger properties, like office developments, industrial facilities, housing complexes, and college campuses, are typically well-suited to it. Even if the lot size is somewhat small relative to the building size, as is typically the case in New York City, a hybrid system can use a modest-sized conventional system to supplement the geothermal approach. Greenhouse gases will be further reduced, as the electrical grid utilizes more wind and solar as opposed to fossil fuels.
In individual settings, ground source heat pump systems work as follows: a pipe network (with closed or open loops) is buried in shallow or deeper ground or alternatively using standing column wells. These approaches circulate fluid to the building’s heat pump system, providing a thermal source for either heating or cooling the facility. In winter, the heat pump extracts heat from the subsurface, while in summer it moves heat from the building back into the ground.
One challenge that must be investigated and engineered thoroughly involves the relationship between the conditions of the land and the requirements for heating and cooling the building. That relationship could require a hybrid system, in which some portion of the heating and cooling requirements are addressed through a conventional system combined with a ground source energy heat pump. In any event, the larger the lot size related to the building’s HVAC requirements, the more feasible it is to install an economical system.
There is a cost to extract and circulate the energy, and there are upfront costs associated with installing the geothermal heat pump system. Financial savings as well as reductions in carbon emissions can both develop over time. In addition, states may provide financial incentives. The State of New York addresses upfront costs through its clean energy investment program.
In creating the New York City tool, Goldman Copeland calculated geothermal ground capacity and potential energy consumption throughout the city, factored in 25 possible building configurations based on vintage, size, and occupancy, and evaluated three different types of geothermal systems. A point-grid method helped determine the potential well quantity for all lots, using both hydrogeological and geological mapping data. Those factors can be adjusted as appropriate for other jurisdictions.
New York City sponsored the modest cost of its screening tool. Presumably, other jurisdictions would do the same.
The adapted tool provides a geographical area with an economical way to screen individual sites within the relevant jurisdiction. Building owners or managers and their engineers could then understand a site’s potential for geothermal energy—how much heating and how many tons of cooling could be obtained from it. The site owner should still do a formal study of the site, but would do so understanding the potential from the outset.
Geothermal energy holds significant promise for reducing carbon emissions in many of America’s cities, suburban areas, and more rural settings. The new Geothermal Screening Tool developed for New York City opens the door for jurisdictions of all sizes to determine their own geothermal potential. In doing so, it enhances the prospects for this future renewable energy source to play a far greater role in combating climate change.
Copeland, PE, LEED AP, is President & CEO of Goldman Copeland Consulting Engineers, a New York City-based consulting engineering firm celebrating its 50th anniversary. One of New York City’s leading experts in innovative engineering, Copeland has created a legacy of reengineering many iconic structures in Greater New York, including Grand Central Terminal and the Alexander Hamilton Customs House, as well as many commercial and institutional buildings. He has earned industry-wide recognition for expertise in mechanical, electrical, plumbing/fire protection (MEP/FP), and energy consulting, distinguishing himself in the management of large, technically complex, and high-profile projects. Most recently, he received the New York Legacy Award from Engineering News-Record.
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