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Why: Benefits of this Typology This layout has advantages in large buildings that are structured to have central piping systems with minimal envelope penetrations and low-power heating units in each room. VRF heat pumps require minimal penetrations for refrigerant piping through exterior walls compared to PTACs or sleeve ACs. This can tighten the building envelope and reduces the overall heating and cooling load. The existing riser space for the steam system can provide potential space for the VRF piping. While VRF systems do have maximum vertical and horizontal lengths of refrigerant piping runs, VRF manufacturers can design piping layouts using VRF plants on intermediate floors for even the tallest and largest buildings. In contrast, residential-scale heat pumps such as mini-splits require relatively short piping runs that present significant challenges for high-rise buildings. Having a central plant means having central control and monitoring capabilities, an advantage for a large building with many apartments. Each manufacturer has a control system for their heat pump technology. These control systems are typically proprietary and not interchangeable amongst manufacturers. Residents get improved temperature zoning and control opportunities in each occupied space and will likely see this as an amenity upgrade. Central heat pump technology brings the option of metering each space and billing residents for what they use, even when utilizing common piping. Buildings with a lot of working capital and the ability to take on a major upgrade can pursue this retrofit. High- rise buildings with market rate apartments, co-ops, or condominiums may be the best candidates because of the ability to meter occupants for heating and cooling costs. Why Not: Plausibility Concerns Current cost estimates for a VRF retrofit start at ~$15 per square foot and double from there, depending on desired system amenities and regional labor rates. Major drivers of cost are the central plant, piping installation throughout the building, which could involve drilling through floors and walls or mounting piping on the exterior of the building, and apartment hardware, possibly including electricity service upgrades (230V) to each room. This cost is substantially more than the replacement cost for a failing steam or hot water plant, which may come in at $1-$3/SF. While a complete heating distribution piping change is considerably more expensive, there are very few buildings that need new steam or hot water piping. Because of the high cost for VRF, large buildings would need to have large existing heating and cooling loads that could be reduced in the retrofit and inexpensive electricity to make this retrofit strategy worthwhile from a financial perspective. The refrigerant concerns detailed in Heat Pumps Use Refrigerants manifest most seriously in VRF systems. Analysis of available installations points toward rates of refrigerant leakage that may affect the systems’ carbon benefit.46 Heat pump systems that utilize split components connected with refrigerant lines have a shorter expected life span than the steam or hot water units they replace. Existing steam or hot water heaters are passive equipment, while new heat pump indoor units are active equipment, utilizing an assortment of electronics, fans, motors, and controls that are fundamentally different from the steam or hot water room heaters being replaced. Central heat pump plant retrofits make the most sense in climates that require both heating and cooling such as Mixed-humid. The mild shoulder seasons may result in coincident heating and cooling loads within a building. To take advantage of this, the VRF system needs to include additional components for heat recovery. This feature adds cost and complexity, and in most multifamily buildings the added cost may not be worth the benefit. The costs and benefits of this additional feature need to be fully evaluated for each retrofit case. Climates with little need for cooling, such as Very Cold and the drier Marine regions, can’t take full advantage of VRF benefits because there is no existing cooling system to improve, making the technology less attractive for the price. Hot climates with little heating load have lower energy cost savings incentive and would not benefit enough from this retrofit compared to other technologies. Steven Winter Associates,Inc. 28PDF Image | HEAT PUMP RETROFIT STRATEGIES FOR MULTIFAMILY BUILDINGS
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CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
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