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Habitat Magazine July/August 2020 free digital issue

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ARCHIVE ARTICLE

Thinking Big With Microturbines

Ever think of installing a microturbine in your building? If you haven’t – and if you don’t even know what a microturbine is – then maybe you should consider it. The system could help protect the environment and – in the long run – put a significant dent in your building’s energy budget. There are new city regulations and ongoing financial incentives that could make it worthwhile.

A microturbine is essentially a gas-powered turbine system that acts as an on-site power generator. The turbines create electricity, which is used to power a portion of a building’s demand. But as a by-product, the turbine system also creates heat that is captured and used to provide portions of the property’s hot water and/or heating needs.

The microturbine is an emerging method of cogeneration, says Dana Levy, program manager for industrial research with the New York State Energy Research and Development Authority, also known as NYSERDA. Combined heat-and-power systems that use engines, not turbines, are more common in the city. “By producing both electric and thermal energy at the same time, cogeneration technology produces more energy from a single fuel source,” says Bruce Beckwith, director of sales and projects for RSP Systems, a distributor of microturbines. Over the past eight years, NYSERDA has offered incentives for about 100 cogeneration projects. About two dozen involve microturbines and only a handful of those are at residential buildings.

One reason for that relatively low number is that microturbines get a bad rap from some. They argue that engines are actually more effective at converting fuel into electricity. Indeed: about 35 to 40 percent of the fuel going in comes out as electricity, while the rest is released as heat. With turbines, about 20 percent of the fuel value releases as electricity while the remaining 80 percent is heat. Also, because of Con Ed rules, microturbines can’t feed power back into Con Ed’s electrical grid, so any power created that isn’t used is essentially wasted.

Because of that, where microturbines are concerned, smaller is sometimes better. NYSERDA’S Levy cites a hypothetical 300-unit building that uses 300 kilowatts (kW) of power during a peak-use period and 100 kW during a low-demand one. Levy says in such a case, he would suggest a 100 kW microturbine system that could “chug along at a constant speed day and night.” Steve Stone, president of DSM Engineering Associates, adds that a 100 or 150 kW system in such a property would generate about 30 to 50 percent of the building’s electrical needs and potentially all of its heat for hot water.

But the system doesn’t come cheap. According to a number of experts, installation of a microturbine can cost between $3,000 and $4,000 per kW. In the 300-unit building, that would mean a $300,000 to $400,000 price tag. Beckwith estimates a three-and-a-half-year return on such an investment; Stone guesses about five years. Of course, as with any project, the ultimate cost will vary based on the size and demand of the building, the condition of the infrastructure, and other factors.

Considering all that, why should a building turn to a microturbine? For one thing, it is better technology for the environment, emitting lower levels of smog-producing nitrogen oxide. Also, because a microturbine supplies on-site power generation, it reduces the demand on power plants. It is more efficient, too: the city says that, for any given amount of fossil fuel, a microturbine will generate 70 to 80 percent of usable energy, while only 30 to 35 percent of energy produced by a power plant is usable.

This may be a good time to consider using one. NYSERDA’s Levy says that his agency aims to distribute about $15 million for microturbines and other cogeneration projects in the next few years. NYSERDA’s cash incentives for microturbine projects in Con Edison territory start at 40 percent of the project’s cost. That incentive bumps to 50 percent if the system is in a building that can serve as a safe haven to others in a disaster, or if it is installed in a way that it can supply power to the building without interruption if the electrical grid goes down.

Another positive factor: the city has recently changed its regulations governing the use of the equipment, which Stone says may even make installation easier. The new rules require microturbine equipment with external gas compressors to have materials and equipment acceptance numbers from the city, which means that the equipment has been pre-approved. Those numbers streamline the applications process with the Department of Buildings (DOB). In all, Stone adds, the DOB “has not been a problem in getting approvals.”

The regulations are the country’s first standards for microturbines, according to Mayor Michael R. Bloomberg. They govern aspects of use and installation, such as the size and placement of the systems, the types of materials used, and the types of permits and inspections needed. “Through the new rule, we have set a standard for the safe use and installation of microturbine systems in residential and commercial buildings where no standard existed before,” says DOB press secretary Kate Lindquist.

DSM has worked on at least 30 multi-family cogeneration projects in the city. DSM’s Stone says microturbine systems installed before the new regulations were imposed are grandfathered in and don’t need to meet the new requirements. However, he points out that his company and others have met many of those standards already, such as those that require gas leak sensors and ventilation.

Stone adds that one of the reasons the city needed to regulate microturbines – and not other forms of gas-powered cogeneration systems – is that the technology requires high-pressure gas. With microturbines, the gas comes into the building at a traditional level of pressure and goes through a compressor so it can be injected into the high-pressure air stream produced within the microturbine.

Finally, if you are thinking of switching, you may ask, where are the success stories? Back in 2004, Millennium Partners, the developer of the Millennium Tower Residences in Battery Park City, decided to install a microturbine to provide a portion of the power and hot water for the 35-story condominium. The microturbine was installed on the roof in early 2006 and residents started moving in December 2006. Charles Norman, project manager in design and construction for the property, says the developer met standards issued by the city’s fire department (FDNY) in early 2007, but had to wait for the city’s regulations, which were created by representatives from several agencies, including the FDNY and the DOB.

At The Millennium, a 60 kW microturbine system was installed for the 234-unit building. Norman says developers expect it to generate about 10 percent of the electrical load needed to power common areas and heat about half of the building’s hot water. The total installation cost for the equipment was roughly $250,000. Because The Millennium is receiving NYSERDA incentives under a program for new construction that covers more than one green project, it can’t break out exactly how much of the microturbine cost will be offset. All told, Norman says the building could receive up to $440,000 for all of its environmental efforts, which also include solar panels, rooftop gardens that capture rainwater, and green building supplies.

“Most of the people in the building don’t know about this yet, but I think they’re going to be happy about it in the long term,” says Norman. “Buildings use energy and energy is getting more expensive. This is going to reduce their energy costs, and it will keep the common charges in check. And that’s a good thing.”

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