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Objective and Motivation

This project intends to devise effective means to further reduce the primary energy consumption of spas to a minimum level ever reported at reasonable costs and to objectively inform spa owners and buyers about energy saving issues.

We have been prototyping different concepts of a "Zero-Emission Spa" which produces even more energy than actually consumed by the spa in standby operation.

The project and its spa prototypes are named "envy", abbreviated from "environment friendly". The envy spas are set-up in a demonstration home - known for its outstanding energy efficiency - for test purposes as well as for demonstration to the public.

Although a range of possible improvements have been suggested by users, their effectivness, however, mostly have been unproperly verified. Within this project we are evaluating and testing those suggestions as well as implementing new ideas and concepts. Tests are performed on high energy efficient standard spas which are subsequently modified and enhanced. Different prototypes will be assessed to their performance.

In 2006 the "California Energy Commission" (CEC) set - almost unnoticed by many spa manufacturers - minimum standards for the whirlpools' energy consumption. According to these new standards many spa models may not be sold any more in California unless their energy consumption is improved (see also http://www.poolspanews.com/2007/091/091title20.html). In the meantime several statets in the US and Europe have followed and set maximum energy consumption levels of spas and/or regulations to offset the energy consumption by domestical produced renenewable energy.

The maximum energy consumption in standby use was set by the CEC to be 5 W x V^2/3 where V represents the water volume in US gallons at a maximum ambient temperature of 15.6°C (60F) and a minimum spa water temperature of 38.9°C (102F). Although many spa models do not comply with this limitation, it has to be stressed, that this limitation is rather moderate and does not reflect the potential of possible energy reduction employing state of the art technology.

Standard test procedures and energy labelling for spas - as already standard for other domestic appliances - is just a matter of time. We hope to support the generation of test standards with our project efforts.