The application of DC grids is gaining more attention in office applications. Especially since powering an office desk would not require a high power connection to the main AC grid but could be made sustainable using solar power and battery storage. This would result in fewer converters and further advanced grid utilization. In this paper, a sustainable desk power application is described that can be used for powering typical office appliances such as computers, lighting, and telephones. The desk will be powered by a solar panel and has a battery for energy storage. The applied DC grid includes droop control for power management and can either operate stand-alone or connected to other DC-desks to create a meshed-grid system. A dynamic DC nano-grid is made using multiple self-developed half-bridge circuit boards controlled by microcontrollers. This grid is monitored and controlled using a lightweight network protocol, allowing for online integration. Droop control is used to create dynamic power management, allowing automated control for power consumption and production. Digital control is used to regulate the power flow, and drive other applications, including batteries and solar panels. The practical demonstrative setup is a small-sized desktop with applications built into it, such as a lamp, wireless charging pad, and laptop charge point for devices up to 45W. User control is added in the form of an interactive remote wireless touch panel and power consumption is monitored and stored in the cloud. The paper includes a description of technical implementation as well as power consumption measurements.
SEEV4-City is an innovation project funded by the European Union Interreg North Sea Region Programme. Its main objective is to demonstrate smart electric mobility and integration of renewable energy solutions and share the learnings gained. The project reports on the results of six Operational Pilots (OPs) which have different scales and are located in five different cities in four different countries in the North Sea Region.Loughborough OP (United Kingdom) is the smallest pilot, being a household with a bi-directional EV charging unit for the Nissan Leaf, a stationary battery, and a PV system. In the Kortrijk OP (Belgium), a battery system and a bi-directional charging unit for the delivery van (as well as a smart charging station for ebikes) were added to the energy system. In Leicester (United Kingdom), five unidirectional charging units were to be accompanied by four bi-directional charging units. The Johan Cruyff Arena OP is a larger pilot in Amsterdam, with a 2.8 MWh (partly) second life stationary battery storage for Frequency Control Regulation services and back-up power, 14 fast chargers and one bi-directional charger. Integrated into the existing energy system is a 1 MW PV system that is already installed on the roof. In the Oslo OP, 102 chargers were installed, of which two are fast chargers. A stationary battery energy storage system (BESS) supports the charging infrastructure and is used for peak shaving. The FlexPower OP in Amsterdam is the largest OP with over 900 EV charging outlets across the city, providing smart charging capable of reducing the energy peak demand in the evening.Before the start of the project, three Key Performance Indicators (KPIs) were determined:A. Estimated CO2 reductionB. Estimated increase in energy autonomyC. Estimated Savings from Grid Investment Deferral
The need to reduce carbon emissions calls for more use of renewable generation, particularly distributed resources. The intermittency of renewable generation, and concerns about energy security, require us to become more independent of central grid operation by use of local or regional (micro-grid) electricity systems. Distributed generation, allied to the commercial availability of battery storage products, permits this–the pathway to energy autonomy. This paper reviews the contribution of different renewable energy sources (RES), trends in energy storage technologies to enable energy autonomy, and the centralised and decentralised techniques that coordinate the associated energy management. The paper covers energy autonomy at different scales, ranging from household levels to district levels. The improvements in grid independency are measured accordingly. There is discussion of this measurement and of the economic and ecological benefits from energy autonomy in the context of policy frameworks.
Thermal batteries, which store and release energy by hydrating and dehydrating salt crystals, hold great promise for domestic heating. Such batteries can be charged from waste heat from industrial processes, and discharged to provide neighbourhood heating. Unlike hot water storage systems, the energy is stored at room temperature, so the thermal losses are very low, making a salt battery highly efficient. However, the electrochemical change of the salt due to hydration and dehydration is very small, making it difficult to measure how much energy is stored in a battery. One promising technique is to measure the absolute humidity of the inlet and outlet air flow. The difference in humidity, combined with a rate equation model allows the total mass of water stored in the battery to be calculated, which can then be used to calculate the energy storage and battery power flow. However, there are several uncertainties in this approach. Commercially available sensors age over time, sometimes quite suddenly. It is not yet known if software can be used to compensate for sensor aging, or if a different sensor type is required. In addition to aging, each measurement is subject to random noise, which will be integrated into the model used to calculate the charge of the battery. It is not yet known how the noise will influence charge estimates. On the other hand, the sensor system must be as durable as domestic heating systems (decades). Hence, it is required to understand sensor aging in order to validate the sensor system for its intended use.
