US national project
The project of the United States is dedicated to the development of a highly-integrated heat pump (IHP)
for Net Zero Energy House (NZEH) application as a co-operation of the Building Technology Program of US
governmental Department of Energy (DOE) and the Oak Ridge National Laboratory (ORNL).
A motivation for the technology development is the strategic goal of the DOE to have market
available net zero energy technology by the year 2020. In this respect, the development is
intended for future implementation and not for today's hous-ing markets.
In a detailed scoping study by Baxter (2005) considering various system layout options,
the IHP concept proved to be the most promising system for NZEH, covering the functionality
for all building services of space heating (SH), water heating (DHW), ventilation (V), space cool-ing (SC),
humidification (H) and dehumidification (DH). An integrated concept incorporating a heat pump has the advantage
of simultaneous production of different building services, e.g. simultaneous SC and DHW in summer operation,
while in stand-alone systems, the heat may be wasted. Thereby, higher investment costs of more energy-efficient
components like variable speed controlled fans are justified, since they are used for multiple functions.
Fig.1 concepts of the groud-source and air-source prototype of the integrated heat pump for Net Zero Energy Houses (NZEH)
An air-source (AS) and a ground-source (GS) IHP has been developed. An overview on the system concept,
energy results and cost estimations by simulations are given in chap. 5.2.3,
a detailed description is contained in the final report on the prototype systems.
Field monitoring of the GS-IHP started in summer 2010, while the field test of the AS-IHP is schedule to begin in winter 2010/2011
as co-operation of the ZEBRAlliance. Details on the field test are documented in a System concept sheet.
Moreover, the US national team has contributed results of the Oklahoma Central Habitat for Humanity field test results
of a housing estate with 16 low energy houses equipped with ground coupled heat pump.
Details on results are documented in a Best Practice sheet.
An accomplished feasibility study delivered the result that a highly integrated heat pump incorporating the functions space heating,
space cooling, DHW, ventilation incl. humidification and dehumidification of the ventilation air is the best option for NZEH.
Therefore, the national project of the USA deals with the development of a highly integrated heat pump configuration.
The work includes prototyping of a unit, lab testing of the different functions and performance simulation studies
with TRNSYS as well as field testing of the unit.