2015-09, Menn, Claudio, Geissler, Achim

Battery energy storage (BES) systems for residential buildings can contribute to power grid stability. The demand for decentralized storage capacity in Switzerland is expected to rise due to political decisions that facilitate renewable energies with power fluctuations such as photovoltaics (PV). Using lithium based BES to meet this demand could have a significant environmental impact as a result of energy intensive production-processes. Furthermore, currently available conventional BES (C-BES) systems are not eco-nomically viable. Within this context, a second use of electric vehicle batteries for 2nd-life-BES (2nd-BES) can be an environmentally sound alternative that facilitates grid integration of residential PV-systems. A model describing the economic viability of 2nd-BES based on the Net Present Value (NPV) method is presented. On the basis of one example building each, results are given for single-family-houses (SFH) and multi-family-houses (MFH), focusing particularly on the market situation found in Switzerland. Results show a cost advantage for 2nd-BES in MFH compared to C-BES systems if a Cycle Life (CL) of 800 and more is available. In SFH, a 2nd-BES shows only a slightly better economic performance than a C-BES system if a CL of 4800 and more can be guaranteed. Notwithstanding the relatively low Levelized Cost of Electricity (LCOE), the NPV for both 2nd-BES and C-BES in both SFH and MFH is negative. Reasons for this are high initial system costs and an electricity tariff scheme with low incentives for con-sumers to store electricity. In this paper, only the current tariff structure in Switzerland is considered. However, alternative tariff schemes, e.g. real time pricing for residential consumers, have become reality in some countries. The impact of such tariff schemes on the economic performance of 2nd-BES is left to future research.

2015-04, Menn, Claudio

Die energetische Bilanzierung von Nullenergiegebäuden findet zumeist auf einer Jahresbasis statt. Diese Berechnungsgrundlage führt dazu, dass saisonale Unterschiede im Energiebedarf und in der Ertragslage erneuerbarer Energien unberücksichtigt bleiben. Für eine Energiewende ist allerdings die Energieversorgung während den Wintermonaten von zentraler Bedeutung. In diesem Zusammenhang stellt das alternative Bilanzierungskonzept mit einer Bezugsbegrenzung ein zielführendes Instrument dar. Es wird in vorliegendem Artikel exemplarisch aufgezeigt, mit welchen bauplanerischen Auswirkungen bei der Einführung einer Bezugsbegrenzung zu rechnen sind.