Governments and companies have set high targets in avoiding CO2 emissions and reducing energy. Aquifer Thermal Energy Storage (ATES) systems can contribute by overcoming the temporal mismatch between the availability of sustainable heat (during summer) and the demand for heat (during winter). Therefore, ATES is an increasingly popular technique; currently over 3000 low temperature ATES systems are operational in the Netherlands. Low-temperature ATES systems use heat pumps to allow the stored heat to be supplied at the required temperature for heating (usually around 40-50°C) and for cooling in summer. Although on average a conventional low-temperature ATES system produces 3-4 times lower CO2 emissions when compared to gas heating, the heat pumps still require substantial amounts of external electricity, causing over 60% of the remaining primary energy use. In the ATES triplet system, the temperatures in the hot and cold wells of an ATES system are increased and decreased respectively to match the required delivery temperatures and a third well is added at an intermediate temperature. With this strategy, other sources of sustainable heat and cooling capacity can supply the subsurface close to the temperatures required in the hot and the cold well. However, the return temperatures from the building systems do not conform with either of the hot or cold wells and an additional well is used to store water at the return temperature. Additional components are then required to supply the hot and cold wells (from the third well) by increasing the temperature in summer (e.g. solar collectors) and decreasing it in winter (e.g. dry coolers). In this study the feasibility of this concept is evaluated. Simulations and an economical evaluation show significant potential for triplet ATES with economic performance better than conventional ATES while the CO2 emissions are reduced by a factor of ten. As the temperature differences are larger, the volume of groundwater required to be pumped is considerably lowered, causing an additional energy saving. Ongoing research focusses on analysing the energy balance and energy loss in the subsurface, well design requirements, working/operational conditions of each well, as well as the integration of building system components, such as the influence of weather conditions on performance of system components.

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For water management in general, it is of high importance to know where, when an how much rain is falling. Especially in urban areas, where water management is of more economic and social import, it is hard to measure the rainfall due to a lack of measurements at the ground. In order to provide a dense gauge network, the sensors need to be reliable, cheap and easy to maintain. The intervalometer aims to cater to this demand. Following (Uijlenhoet and Stricker 1999), all rainfall related parameters can be tied together using one parameter (mm􀀀1), which characterizes the raindrop size distribution (DSD). This parameter can subsequently be related to the raindrop arrival rate A (m􀀀2 s􀀀1) at a surface A(m2). The raindrop arrival rate can be measured by registering the intervals between the drops hitting a piezo element. The concept of the Intervalometer is tested by using data acquired in Bago, Myanamar (monsoon season) and in the Netherlands. The DSD, the rain rate, and the rain depth are calibrated and validated with respect to other rain gauges present (e.g. disdrometer, tipping bucket). It is assessed that the validation sets of the rain rate and rain depth show a high coefficient of correlation of respectively R2 > 0:85 and R2 > 0:98. In addition the root mean square errors are limited to less than 1mm per hour. The low costs and the simplicity of the Intervalometer show a high potential for providing a dense rain gauge network in areas where there is an increasing demand. This project is co-funded by the European Union through Project 776691 “TWIGA”. @en

Crowdsourcing as a method to obtain and apply vast datasets is rapidly becoming prominent in meteorology, especially for urban areas where routine weather observations are scarce. Previous studies showed that smartphone battery temperature readings can be used to estimate the daily and citywide air temperature via a direct heat transfer model. This work extends model estimates by studying smaller temporal and spatial scales. The study finds the number of battery readings influences the accuracy of temperature retrievals. Optimal results are achieved for 700 or more retrievals. An extensive dataset of over 10 million battery temperature readings for estimating hourly and daily air temperatures is available for São Paulo, Brazil. The air temperature estimates are validated with measurements from a WMO station, an Urban Flux Network site, and data from seven citizen weather stations. Daily temperature estimates are good (coefficient of determination ρ² of 86%), and the study shows they improve by optimizing model parameters for neighborhood scales (< 1 km²) as categorized in local climate zones (LCZs). Temperature differences between LCZs can be distinguished from smartphone battery temperatures. When validating the model for hourly temperature estimates, the model requires a diurnally varying parameter function in the heat transfer model rather than one fixed value for the entire day. The results show the potential of large crowdsourced datasets in meteorological studies, and the value of smartphones as a measuring platform when routine observations are lacking.

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Bodemenergiesystemen worden veelvuldig toegepast om energie te besparen. De warmtepomp van zulke systemen gebruikt echter nog altijd veel elektriciteit, waardoor voor grootschalige toepassing ook grootschalige netverzwaring nodig is. Daarom is het voor de verduurzaming van de gebouwde omgeving belangrijk om alternatieve duurzame technieken voor verwarming en koeling van gebouwen te vinden. Het WKO-‘triplet’-systeem vermijdt elektriciteitsverbruik door de warmtepomp door warmte en koude op het gewenste temperatuurniveau in te vangen en in de bodem op te slaan met (bijvoorbeeld) zonnecollectoren en droge koelers. Het primair energieverbruik van een tripletsysteem is ongeveer 5% van een conventioneel systeem.@en