Geothermal, Solar

RFP Issued to Improve Earth Energy Installations

One of the largest engineering groups in the world will pay US$120,000 to develop guidelines that make earth energy systems better and reduce their costs.

ATLANTA, Georgia, US, 2001-04-12 <SolarAccess.com> The American Society of Heating, Refrigerating & Air-Conditioning Engineers (ASHRAE) wants guidelines for the selection and design of the pumping and piping subsystems for ground-coupled heat pumps. The systems transfer solar energy from the surface of the ground into a building for space heating and water heating, and can be reversed in summer to provide cooling. The technology is recognized in the United States, Canada and most other countries as a renewable energy, but the high first cost to install the loop constitutes the majority of the system cost and acts as a major barrier to market penetration. “The goal of every geothermal heat pump system designer is to find an optimum balance between capital costs and operating and maintenance costs,” says the RFP. Engineers often apply their knowledge from central chilled water systems, central boilers and cooling towers to the design, but heat pumps “have a uniquely different set of design constraints and positive attributes that can be compromised when conventional water loop piping practices are selected.” This study is designed to examine ways to reduce capital costs, as well as operating and maintenance costs of pumps and piping specific to earth energy systems, without increasing heat pump energy consumption. The ultimate goal is to develop design criteria for cost effective pumping operation. “The characteristics of ground loops and their associated components are significantly different from other types of heat exchangers, and from the plumbing and piping systems typically seen in other HVAC applications,” it explains. “These differences impact the selection of flow rates, allowable head losses, and piping materials.” There are some very rudimentary guidelines concerning pumping in conventional chilled and hot water systems, but these do not specifically address earth energy systems. Unlike conventional systems where a pump circulates water from a central boiler or chiller to heating and cooling coils, the situation for a heat pump is reversed and the circulating pump circulates fluid from the ground. ASHRAE estimates that the energy for pumping in an earth energy system can be from 15 to 48 percent of total consumption when the pumps operate continuously. “Geothermal heating and cooling systems, as well as hybrid geothermal/cooling tower systems are finding increased applications in a wide variety of buildings,” it explains. “Engineers currently do not have many of the tools necessary to quickly and accurately identify the optimum pump/piping system.” The project will survey the capital and operating costs of alternatives for pumping in geothermal heat pump systems, and simulation models will be developed for each alternative for representative buildings and climates. The report will provide recommendations on the most economical pumping/piping system based on climate and load diversity, and these recommendations will be embodied in design tools. ASHRAE has 50,000 members around the world. Proposals are due by May 18, and projects must start by September.