Electricity Usage in Smart Village Skarpnes

The goal of the project "Electricity Use in the Smart Village Skarpnes" was to examine how the electrical distribution network can be designed and managed in an optimal way in the future. Low energy houses with local energy production from photovoltaic (PV) systems have different requirements for power capacity in the grid. New energy efficient appliances can have very high demand for power. Line charges (nettleie) now cost more than charges for electrical energy. Therefore, we need to manage maximum power demand, kW, as well as energy efficiency, kWh. The project collected data from five near zero energy houses built at Skarpnes, south of Arendal. Skanska built the houses in 2014 and 2015. This data is unique because it is the first zero-energy housing development in the Nordic countries. The houses were equipped with instrumentation that detected real consumption data. The PV system production was monitored along with irradiance and temperature and PV system performance was calculated. The electrical consumption and production of each house was continuously recorded by a high resolution Elspec meter and an AMS type meter. Such comprehensive data is not available from any other known source in Norway. Annual net energy use by the Skarpnes houses has not met the near zero energy goal, however, the net annual energy consumption is much lower than a typical Norwegian house. Feedback from the house owners confirms that the houses are very comfortable to live in. There is variation in the net energy consumption between the five houses. This has several causes: personal preferences, set up of heating and ventilation control systems and use of the systems including added plug-in loads. The annual net energy use appears to be decreasing, which suggests that optimizing the control system is possible. The project collaborated with Scanmatic for the design and installation of the technical measurement equipment, and cooperated with the following separate research projects lead by Sintef: ZEB - Research Centre on Zero Emission Buildings, and EBLE - Evaluation of housing with low energy requirement. The PV systems are producing slightly more energy than predicted. The houses have different orientations in azimuth angle (East-West), which results in small differences in the production profiles. This gives insight into coincidence factor variations between PV production and consumption for otherwise near identical conditions. The University of Agder and Teknova have in collaboration with Agder Energi Nett developed procedures for pattern recognition to identify power peaks in consumption profiles for electricity customers. Individual and aggregated power demand were investigated to determine how the distribution grid will be affected by zero-energy houses in the future. This is critical information for Agder Energi Nett to plan future net operations. Maximum power consumption is more than ten times the average. Therefore, power management technology has the potential to make a large reduction in the future cost of new grid capacity. Grid capacity is based on the combined power consumption for groups of houses. Because maximum power consumption did not occur simultaneously among the five houses, the maximum power for the five houses is very rarely more than 2.5 times the maximum power consumed by any one of the five houses, instead of 5 times. Grid capacity also needs to be sufficient for the combined export of power from a group of houses. Although maximum solar production did occur simultaneously among the five houses, the maximum export power for the five houses is about 5 times the maximum power exported by any one of the five houses, which is 7 kW for the Skarpnes houses. The Eltek Energy Storage System, ESS, has been operating since late 2015. The ESS has demonstrated that maximum power demand can be limited and alternatively, self-consumption of solar power can be maximized. The inverters in the system also have the capability to improve power quality through balancing phases and stabilize voltage through reactive power adjustments. The Skarpnes data shows that excessive neutral phase currents can occur when power is imported and exported simultaneously on different phases. The main cause of large neutral phase currents is not-balanced phases. Solutions are 1) to avoid large single-phase loads, or 2) install storage systems and PV systems which use inverters that have the capability to balance power in the three phases. The Skarpnes data also shows that when the power in the phases are not balanced and power is imported and exported simultaneously on different phases, both energy tariffs and power tariffs must be based on measurements from each of the three phases. Basing tariffs on total energy or total power will not result in the correct charges for prosumers. This is important for future business models and operation of the local grid.

The present project aims to supplement two large on-going research projects on Smart Grids in Norway, Demo Steinkjer and Smart Energi Hvaler. Complementary data and results will be collected by monitoring the electricity use in 5 zero houses all of which will produce electricity with solar cells. The houses are located at Skarpnes in Arendal and were built by Skanska. Norwegian authorities plan to introduce the passive house standard as a requirement for new buildings from 2015. To be able to dimension the electricity grid in areas dominated by passive houses it is necessary to learn how load profiles in passive and zero houses differ from those of traditional houses. In 2020 the building regulations might be even stricter, as there are plans to introduce zero energy buildings as a requirement for new residential buildings. This will enhance the need for new modeling tools for grid planning, tools that must take into account the electricity production from distributed electricity generation as well as new load profiles. By 2019 the plan is that all electricity consumers must have installed meters registering their electricity consumption every 15 minutes. Seen in combination with the above mentioned changes in energy performance of new houses, this outlines a future with new opportunities and challenges for the grid operators. In the research project "Electricity usage in Smart Village Skarpnes" data from automatic metering systems, AMS, will be used to monitor load profiles and electricity production in the new zero energy houses at Skarpnes. Additional high performance meters will monitor demand and production from the five houses and the local substation, at a very high frequency so that power quality can be monitored. A residential-size electrical- storage system is also connected to the system. This provides data on the critical issue of load shifting for demand management. The site offers a unique opportunity to study a number of buildings to prepare for the future. The project is gaining experience and data that will be used to plan the future electricity grid. Expansions and up-grades of the electricity grid are expensive so careful and accurate planning will be of great value for the distribution grid operators.