Abstract
The utilization of groundwater heat pump systems is increasing in Norway, which are currently widely employed for heating and cooling applications in the town center of Melhus. The investigations of the Melhus installations are detecting gas exsolution as a possible trigger for precipitation reaction that causes incrustation of iron and manganese compounds in the systems. This paper discusses risks associated with gas exsolution and considers gas exsolution triggers in a typical Norwegian groundwater heat pump (GWHP) system configuration. The concept of the solubility grade line (SGL) is developed and suggested as a tool for optimizing the design. Based on SGL analysis and the intention of avoiding gas exsolution during heat production, an alternative system design in the same aquifer is presented and compared. The analyses show that the traditional system design is predisposed to gas clogging risks and prone to vacuum pressures in parts of the system. The alternative design mediates the risks by adjusting the well and piping configuration and by applying a backpressure technique. The results demonstrate how the groundwater heat pump system design can be customized according to local aquifer conditions to avoid gas exsolution during operation. It is recommended that the presented method of analysis should be utilized in dimensioning of systems and included in the monitoring scheme of the systems.
Highlights
Ground source heat pump (GSHP) systems have become increasingly popular in Norway during the recent decades
Theenergy location of the heat exchanger to athe heat pump unit,the contributing to an as short as is re-injected intoloop the of aquifer with fluid, a higher temperature than the original e.g.,and an possible indirect secondary yielding lower costs associated withtemperature, the indirect loop increase from the circulation of secondary fluid. This might be convenient in many installations, but if the distance pump is at great, 10 m above the production well screen triggers a pressure of fromThe the location wells to of thethe building the length of the groundwater loop can sometimes bedrop several
The gauge pressure head grade line (GPHGL) analysis along the dotted line a line (A–I) in Figure 5 shows that the traditional system configuration is predisposed to losses of pressure after the groundwater has entered through the production well screen (Figure 7)
Summary
Ground source heat pump (GSHP) systems have become increasingly popular in Norway during the recent decades. Among a wide range of GSHP concepts, groundwater heat pump (GWHP) systems, known as open loop GSHP systems, are unique because they extract thermal energy directly from groundwater rather than via heat collectors in soil or bedrock formations These systems are less common than closed loop GSHP systems, but GWHP systems provide an efficient and cost-effective alternative in areas where the local hydrogeological conditions are favorable, especially for medium to large facilities (>100 kW heating capacity systems) and for facilities with large annual cooling demands. Observations and investigations in Melhus by Brøste [3] have revealed gas bubbles in the groundwater during groundwater sampling, similar to some of the observations of Yon-Gyung et al [14] in a CO2 storage site in Korea This arguably points towards gas exsolution as a possible cause for some of the clogging and fouling problems found in Melhus. The new strategy provides an alternative approach to the traditional Norwegian GWHP design methodology and focuses on preventing or limiting the risk of gas exsolution
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
