Jennifer V. Hughes in Green Ideas on April 8, 2016
The massive Roosevelt Terrace co-op in Jackson Heights, Queens, has done something nearly miraculous. They’ve cut their energy usage by 59 percent, resulting in annual savings of about $360,000.
How did they do it? The short answer is: cogeneration, otherwise known as combined heat and power acceleration, or CHP.
Cogeneration is a system that simultaneously generates electricity and usable heat. When electricity is produced, some energy is discarded. But in cogen, much of this wasted heat is captured and used to heat domestic hot water.
While most buildings are good candidates for cogen systems, there are some qualifications that have to be taken into consideration, says Gregg Giampaolo, president of All Systems Cogeneration. You need to have adequate demands both from your thermal (hot water) and electrical set-ups. If your only need for hot water is to supply domestic water in the apartments, for instance, that can be a strong enough load if you have enough units.
Similarly, on the electrical side, if your building is submetered – meaning that each unit has its own Con Ed meter – the building-wide draw is only in the common areas. That’s not always a deal-breaker. If those common areas provide enough of an electrical demand, a cogen system can still work. In general, master-metered buildings – where the common areas and all the in-unit electricity are bundled together – are the easiest sell for cogen.
While there are many different factors that have to be considered with cogen, Giampaolo says that a building with a 75 kW system would need at least a 60,000 kW electrical load monthly, and a thermal load of about 3,000 therms per month. (That’s usually about 200 apartments.)
The project at the 4,370-unit Roosevelt Terrace co-op was installed alongside the existing boilers. The first phase – two separate 75 kilowatt (kW) systems – went online in July 2012 in Buildings 1 and 2. The kW size is tied to the electrical demands; more power or hot water needed equals larger-sized units. The second phase, underway now, will use a unique solution that involved installing a single 100 kW unit to power both Buildings 3 and 4. It is expected to be online in time for the summer air conditioning load.
The cogen now in place is supplying enough electricity so that Roosevelt Terrace is purchasing only about 900,000 kW from Con Ed for common areas and in the apartments. When it comes to benefits from hot water, the Phase 1 cogen system actually supplies all four buildings’ hot water load during the summer (when a warmer base-water temperature makes it more efficient to make hot water) and about half of the load during winter months.
“Adding Phase 2 will make enough hot water for all four buildings during the dead of winter,” says the co-op board’s president, Ed Ermler, an electrical engineer. Phase 2 will also allow the co-op to use the heat thrown off during the production of electricity in another way. Ermler says that after hot water runs through the system into apartment radiators, it normally goes back into the system at about 80 to 90 degrees. By passing it through the cogen unit, that heat thrown off during the process will return that water back to the boiler hot enough so that it is almost “steam ready.” As a result, the whole system is more efficient.
“The best advice I can give to the layman is to hire a competent engineering firm to do your Local Law 87 work and produce a competent report that identifies where you can save money,” Ermler says. “Almost every project I’ve seen includes cogen because it makes perfect sense. It’s one of the easiest things to do, especially with the incentives out there.”
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