Optimization and spatial pattern of large-scale aquifer thermal energy storage
Sommer, W.T. ; Valstar, J. ; Leusbrock, I. ; Grotenhuis, J.T.C. ; Rijnaarts, H.H.M. - \ 2015
Applied Energy 137 (2015). - ISSN 0306-2619 - p. 322 - 337.
source heat-pumps - geothermal systems - ground-water - transport - consumption - simulations - performance - buildings - solute
Aquifer thermal energy storage (ATES) is a cost-effective technology that enables the reduction of energy use and CO2 emissions associated with the heating and cooling of buildings by storage and recovery of large quantities of thermal energy in the subsurface. Reducing the distance between wells in large-scale application of ATES increases the total amount of energy that can be provided by ATES in a given area. However, due to thermal interference the performance of individual systems can decrease. In this study a novel method is presented that can be used to (a) determine the impact of thermal interference on the economic and environmental performance of ATES and (b) optimize well distances in large-scale applications. The method is demonstrated using the hydrogeological conditions of Amsterdam, Netherlands. Results for this case study show that it is cost-effective to allow a limited amount of thermal interference, such that 30–40% more energy can be provided in a given area compared to the case in which all negative thermal interference is avoided. Sensitivity analysis indicates that optimal well distance is moderately insensitive to changes in hydrogeological and economic conditions. Maximum economic benefit compared to conventional heating and cooling systems on the other hand is sensitive, especially to changes in the gas price and storage temperatures.
Toluene biodegradation rates in unsaturated soil systems versus liquid batches and their relevance to field conditions
Picone, S. ; Grotenhuis, J.T.C. ; Gaans, P. van; Valstar, J. ; Langenhoff, A.A.M. ; Rijnaarts, H. - \ 2013
Applied Microbiology and Biotechnology 97 (2013)17. - ISSN 0175-7598 - p. 7887 - 7898.
vapor intrusion - vadose-zone - aerobic biodegradation - petroleum-hydrocarbons - numerical-model - carbon-dioxide - water-content - new-jersey - kinetics - benzene
Contaminant biodegradation in unsaturated soils may reduce the risks of vapor intrusion. However, the reported rates show large variability and are often derived from slurry experiments that are not representative of unsaturated conditions. Here, different laboratory setups are used to derive the biodegradation capacity of an unsaturated soil layer through which gaseous toluene migrates from the water table upwards. Experiments in static unsaturated soil microcosms at 6-30 % water-filled porosity (WFP) and unsaturated soil columns at 9, 14, and 27 % WFP were compared with liquid batches containing the same culture of Alicycliphilus denitrificans. The biodegradation rates for the liquid batches were orders of magnitude lower than for the other setups. Hence, liquid batches do not necessarily reflect optimal conditions for bacteria; either oxygen or toluene mass transfer at the cell scale or the absence of soil-water-air interfaces seemed to be limiting bacterial activity. For the column setup, the rates were limited by mass supply. The microcosm results could be described by apparent first-order biodegradation constants that increased with WFP or through a numerical model that included biodegradation as a first-order process taking place in the liquid phase only. The model liquid phase first-order rates varied between 6.25 and 20 h(-1) and were not related to the water content. Substrate availability was the primary factor limiting bioactivity, with evidence for physiological stress at the lowest water-filled porosity. The presented approach is useful to derive liquid phase biodegradation rates from experimental data and to include biodegradation in vapor intrusion models.