Analysis of building energy use and evaluation of long-term borehole storage temperature : Study of the new ferry terminal at Värtahamnen, Sweden

Sammanfattning: In 2013, Stockholms Hamnar began a development project for Värtahamnen, one of Stockholms most important harbors, and also decided to build a new ferry terminal that is better suited to meet the increasing capacity demand. The new terminal will feature a borehole storage that will be used to cover the building’s heating and cooling demands. The boreholes have already been drilled and currently the construction of the building is being planned. The overall objective of this project is to study the new terminal and its borehole storage regarding certain input parameters (such as internal heat gains and the U-value of windows) that affect the building’s annual heating and cooling demands, as well as long-term temperature of the borehole storage. To do this, two modeling programs are used: IDA ICE and EED (Earth Energy Designer). The project focuses on three main parts. Part one is a sensitivity analysis of internal loads and construction specific parameters that shows how a variation in these affects the heating and cooling demands. To accomplish this, several models are created and simulated in IDA ICE. In part two, the long-term ground temperature is studied for two of the models analyzed in part one. This is done in both IDA (through a new borehole module) and EED, followed by a comparison of these results. The last part presents the possible amount of free cooling that can be taken from the ground. This estimation is made through simulations in EED, using altered load profiles of the two previously mentioned models. Additionally, this part covers the effects of a changed borehole configuration (number of boreholes, depth, layout, etc.). The results of the first part (the sensitivity analysis) show that there is a rather large variation in annual heating and cooling demands depending on what approach is used for estimating a reasonable amount of internal loads. One way to do this is to first determine the maximum possible load in each zone and then, when simulating the annual energy demand, reduce the total load in the whole building by a certain factor. Another approach is to, from the start of the building modeling, more accurately try to estimate the average amount of internal loads in each zone. In the second part, due to unbalanced load profiles for both analyzed models, the temperature of the borehole storage will increase over time if there is no limitation of the amount of cooling taken from the ground. The results of IDA generally agree with those of EED. In the last part of the project it is shown that a thermally more favorable borehole installation could increase the relative amount of free cooling from the ground, compared to the current installation.