**6. Modern technologies prospects for vacuum heating systems in tall buildings**

#### **6.1 Plumbing**

All existing steam/vacuum heating systems employ heavy steel piping. ESB plumbing contains 50 miles of radiator pipes, including 24 inch (1 inch = 2.54 cm) risers, and 7000 cast iron radiators. Soldered copper tubing was restricted from steam/vacuum heating because rapid heating caused cracks in the soldered joints. Modern ProPress plumbing method employs no soldering, slash installation time and is backed by a 50-year warranty against rust, defects in material and workmanship. Furthermore, the piping diameter/weight is reduced drastically; also reduced is heat loss, the amount of condensate in pipes, and heating time compared to steel piping. In the NGRID study, the 2 ½" steel pipe at the steam boiler exit was replaced by a ¾" copper tube – this resulted in an 11.5 fold drop in price and 16 fold drop in weight (please note this also corresponds to a 16 fold drop in the system preheating time and condensate amount).

Another plumbing option is thermoplastic piping, − no rust, easily glued, quickly assembled, and leak-proof. An Aquatherm polypropylene piping system operates at temperatures up to 200°F (93°C) at 15–100 psig (1–6.8 atm), so technically it should handle saturated water vapor at 6"Hg/200°F (93°C) without any problem. Like Propress, Aquatherm is backed by a 50 year warranty, and available at larger diameters (up to 300-600 mm). Polysulfone thermoplastic is already approved for low pressure steam systems in the US – up to 230°F at 15psig, it can be welded, sawed, and glued like Polyvinyl Chloride plumbing.

Clamped silicone/rubber fittings can be utilized for plastic piping; additional benefits include easy assembly/disassembly/repairs/adjustment, compensation for thermal expansion/contraction, and noise reduction. A polysulfone tube with clamped silicon fittings worked in a tested vacuum heating system for 3 winters without any problem. Liquid Crystal Polymers with heat deflection temperature of 290C can be utilized at higher temperatures.

Modern methods of leak detection allow annual proactive testing to find new leaks and keep the system operational for many years. Needless to say, thermoplastic piping with no rust/oxidation problems is of low maintenance and easy to repair.

#### **6.2 Cast aluminum radiators**

In steam heating systems pipes accounted for 30–35% of the total system weight and have to be reheated to 214°F every heating cycle. To reduce the heat loss of pipe reheating, heavy radiators are employed to accumulate heat. This archetype can be dismissed if much lighter copper or polymer piping is utilized.

Modern cast aluminum radiators present a much less expensive, lightweight alternative, they are slim, modern looking, have a modular design (length adjustable) and warrantied for up to 20 years at a pressure 7 atm [SIRA]. Such radiators by SIRA have been working problem free in a tested vacuum heating system since 2015 [26].

#### **6.3 New control paradigm**

Presently, vacuum heating systems control heat distribution via control valves on the supply lines. These are expensive items because of steam rating and large pipes diameters. Instead, the new technology employs control valves on smaller diameters vacuum lines in order to direct steam into the required system partitions. Normally open valves close when the vacuum line temperature rises above 30-40°C and are never exposed to hot vapor so a long life span is expected. Closed valves prevent air removal from a particular radiator(s), and therefore result in only partial heating (similar to TRV operation). Heat distribution and a sequence of heat supply into system partitions can be dynamically controlled.

Instead of radiators, air handlers on every floor and heat exchangers for distributed hydronic subsystems can be employed in new installations. Compared to hydronic only system, a significant size reduction of air handlers and heat exchangers can be achieved due to higher steam specific heat capacity, linear velocity and better heat transfer. Vacuum heating system plumbing for such "hybrid" systems would be simplified and heat distribution would be controlled easier. An additional benefit would be the possibility of per floor/apartment heat consumption metering in distributed subsystems, which is problematic in steam/vacuum systems.

#### **6.4 Cogeneration heat and power (CHP) benefits and geothermal outlook**

Steam/vacuum heating can be readily integrated into CHP, the most reliable and efficient electricity and heat source. In high efficiency power plants, a steam turbine exit is connected to a condenser to extract maximum electricity. The vacuum in a condenser is created via steam condensation by cold water. If the building vacuum system is connected instead of a condenser, this additional electricity would be received without steam and cold water expenditures, cooling tower, pumps, etc. In summer time, any excess steam of high temperature can be utilized in an adsorption cooler on the roof (more efficiently than hot water). Again, no electricity wasted on pumping water.

Steam is a by-product of untapped green technology - geothermal heat. "2000 times US annual energy use could be supplied indefinitely 24/7 using existing

*Steam Heating Conundrum of High-Rise Buildings DOI: http://dx.doi.org/10.5772/intechopen.108107*

Engineered Geothermal Systems (EGS) and perhaps 10 times as much with improved technology" [27]. At 5.5 km depth, 175-225°C heat source can be reached on the most of the US west part, and 100-150°C on the east part. A mature EGS can supply enough electricity for 800 to 41,000 average U.S. homes or dozens high-risers. The \$5-10 M cost of drilling (4 and 6 km deep well, correspondingly) [28] is not an outrageous expense for reliable heat and power source compared to \$7-20 M average floor price tag for high-rise in Chicago and NYC [29]. At 500% efficiency [30] this opportunity dwarfs the promises and attractiveness of HP, wind and solar power.

### **7. Conclusion**

The US is not alone in dealing with steam heating upgrades, steam is also widespread in Europe [8] and China [31]. Worldwide there are thousands of steam heated buildings, including high-risers, which would benefit from a simple, efficient and reasonably inexpensive conversion into vacuum heating. Modern plumbing technology and materials makes vacuum heating a very attractive choice for new installations as well.

It's not unusual that old technology gets a second chance thanks to the progress in knowledge and materials. In 1893, electric cars lost the Paris-Rouen race and they have made a magnificent comeback since then. Who is to say that will not happen to vacuum heating technology for new buildings, especially skyscrapers?

#### **Acknowledgements**

The research on NextGen vacuum heating was inspired by Dan Holohan books and advice, supported by Kith Miller of NGRID and Ed Infantino of A&M SERVICES.

### **Abbreviations**


*Recent Updates in HVAC Systems*
