Visitors to the landmark Ritz-Carlton in San Francisco won't hear the low whirl of microturbines generating electricity from what was once a courtyard work shed. Nor will they notice that the air is cooled by UTC Power's new PureComfort dual action absorption chiller. Nonetheless, the hotel's owner, the Host Marriott Corp., has noticed a marked improvement in energy efficiency and lower emissions since implementing the new combined cooling and heating power solution.

Purchasing the PureComfort system was the result of an ongoing plan to lower energy consumption at the hotel, according to Paul Savarino, Ritz-Carlton director of engineering. “We were looking for any means to save energy,” says Savarino. “Host Marriott wanted to put a UTC system in one of their hotels, and we have the room and the perfect climate for the microturbines, because they work best at around 40 to 50 degrees Fahrenheit.”

Host Marriott chose UTC Power's 240M configuration, a combination of four 60-kW Capstone microturbines and a double-effect absorption chiller from Carrier Corporation, UTC Power's sister company. The chiller collects the microturbine's exhaust in a manifold and puts out 161 refrigeration tons (RT) of cooling at an ambient air temperature of 59 degrees.

With the hotel's electricity demands running as high as one MW, and chilling requirements that can reach 300 RT, the decision to use UTC Power's smallest unit might seem odd. Why choose the configuration of four microturbines when UTC Power offers a 300M (five microturbines) or 360M (six microturbines) system, with chilling capacities of 188 and 210 RT respectively?

“The beauty of this system is that we can base-load the chiller year-round,” answers Mike Vukovinsky, UTC Power's director of onsite power products and applications. Moreover, the chiller's output achieves its highest efficiencies in chilling mode, and even when San Francisco's foggy day's drop below 59 degrees, there's no need to switch it over to heating mode. “We're fortunate enough in this application to have the chiller base loaded,” Vukovinsky adds. “With this utilization we expect to see the overall efficiency of the system reaching 82 to 83%.”

It's not surprising that large hotels have a demand for year-round chilling. According to Savarino, restaurants and kitchens create most of the heat. Before the PureComfort installation, the Ritz relied on a 300-ton electric chiller to deal with that heat, but it was an inefficient arrangement—and expensive.

The original unit ran 24 hours per day and accounted for 20% of the hotel's electricity consumption. Savarino says the hotel incurred excessive energy bills by running a 300-ton chiller on the many days when demand dropped as low as 100 tons. Now he anticipates shutting down the 300-ton unit for a third of the year, using it only to supplement the PureComfort system during the hottest months of summer. “With a little bit of luck we may not have to use the original chiller during the months of October through March,” he adds.

The 336-room luxury hotel occupies an entire city block.

With an electricity load that typically ranges from 400 kW to 1 MW, the Ritz will see a substantial savings in electricity. The microturbines run on natural gas, and, though gas prices have risen, the fact that the chiller requires only waste heat still offers an appreciable economic advantage. “When we sold the system, their gas rate was $6.60 per decatherm, and now it's $8, so the payback is about three years,” says Vukovinsky. His estimate includes the hotel enjoying a reduction of $140,000 in electricity at a current rate of 12 cents per kilowatt-hour.

Installation of the PureComfort system went surprisingly well, considering the age and status of the structure. Located in the upscale Nob Hill area of San Francisco, the building began in1909 as the West Coast headquarters of the Metropolitan Life Insurance Company. Later, it became the main campus of a local college, and in 1984 it was designated a city landmark and deemed an “architecturally significant structure.” But its significance and landmark status didn't save it from falling into a state of disrepair.

Nonetheless, Ritz-Carlton recognized the potential of such prime real estate, and because the space was never designed to provide overnight accommodations (nor did it meet current building codes), the structure's entire interior was demolished in 1997. Then came an extensive, four-year renovation before reopening the landmark as a 336-room luxury hotel that occupies an entire city block.

Savarino says that PureComfort's size was an advantage and remembers the task of transporting the equipment through Nob Hill's tight streets as being more challenging than the actual installation. The PureComfort 240M has a footprint approximately 22 feet long, 21 feet wide, and 16 feet high. The chiller weighs 18,544 lbs.; each microturbine weighs 1,700 lbs. The system is modular and uses the same chiller for the 240, 300, or 360 microturbine combinations.

Access to a courtyard building simplified the site placement, but retrofitting makes for a more complicated project, explains UTC Power's president, Jan van Dokkum. “If it's a retro there's more custom work because we don't have the space, and equipment rooms are always quite small to begin with,” says van Dokkum. “So we need cooperation between the building owner and facility operator. We start with calculations for the kind of system needed, then the demand of the existing systems, and finally there's the planning for the easiest installation. We do a lot of legwork at the site, with close cooperation of the facility managers.”

Legwork was the operative word in reference to San Francisco's grid. The project required an interconnection to a spot network within the PG&E distribution grid. The interconnection protection design incorporated a microturbine load following control to prevent incidental export to the grid. Additionally, microturbine (under power) relaying was incorporated and coordinated with changes to the PG&E network to safeguard the operation and ensure highly reliable power.

“San Francisco is on a network system as opposed to a radial system,” explains van Dokkum. “So it's a little more complicated because the existing standards for the interconnection, which are IEEE 1547, generally don't apply to those kinds of networks. So you really have to work closely with the utility to make sure you have the right network connections and relay sensors that won't upset the grid.”

Vukovinsky adds that UTC offers the PureComfort for grid connect or dual mode operation. “For the Ritz we did a grid connect, so if the grid goes away the system shuts down,” he explains. “In other installations we have dual mode that also functions as a backup. There's a choice to be made between the two, and the facilities manager weighs the cost to his operation if he loses power. What are the costs to a grocery store for food spoilage and those associated with a power outage?” Also, facility managers must consider the higher price of dual mode operation resulting from extra equipment and controls such as relays and switches required on the electrical system.

The Ritz preferred the simplicity of a grid connect, says Savarino. “The beauty of it is that if for some unfortunate reason it goes down, there's no impact to the hotel, because it's a standalone system and nothing is dependent upon it.”

Both van Dokkum and Vukovinsky don't expect the PureComfort to go down, largely because of UTC Power's remote monitoring service. “We monitor all of our equipment online, so we know before the customer knows when there's anything unusual in the system,” says van Dokkum. “And we're relying on the Carrier Service Network, which is all over the country.

So far, service calls have been few for the company's current installations (see sidebar). Vukovinsky recalls a clogged filter on a microturbine and voltage problems from fluctuation current on the grid. “What we're talking about is the ability to dispatch service on a 24/7 basis,” he says.

Paul Savarino notes that his engineers will train on the PureComfort system, but their responsibilities won't include major maintenance. He likes the remote monitoring and wants to expand upon the concept with a total energy management solution for monitoring and controlling all energy consumption at the Ritz Carlton. “Energy usage and reduction is one of my main goals,” says Savarino. Then, too, there's the benefit to Host Marriott in its goal to maintain an image as an environmentally green corporation. The Ritz can claim a reduction of emissions equivalent to removing 250 cars from the roadways per year.

Such goals are all good news to van Dokkum. The Ritz is the first hotel installation for UTC Power's PureComfort, and van Dokkum says the hotel industry is a prime market for his company. And in a nod to the growing number of fuel cells in hotels, he notes that the PureComfort could be powered by fuel cell exhaust.

ED RITCHIE is a writer specializing in energy and communications technologies.

DE - March/April 2006