Demand-side Flexibility in Smart Grid by Roya Ahmadiahangar & Argo Rosin & Ivo Palu & Aydin Azizi

Author:Roya Ahmadiahangar & Argo Rosin & Ivo Palu & Aydin Azizi
Language: eng
Format: epub
ISBN: 9789811546273
Publisher: Springer Singapore

In grid-connected nZEB the flexible loads are defined as loads that can be shifted from a high tariff period to a low tariff period without any investments to additional electrical or thermal energy storage. Depending on the electricity market prices the set point for the thermostatic control will be calculated for each time step. In on-grid systems with the combination of the optimum price-based control algorithms, it is possible to save about 20% of the costs for the appliances’ energy consumption. Depending on amount of flexible load in the building, it could be also 10–20% of the electrical energy costs of the apartment. [26] reported that HEMS could reduce the operational cost of electricity by 23.1% on average, or reduce residential peak demand by 29.6%.

The coordination between different priced based DR programs of nZEBs is vital to maintain the grid efficiency. Otherwise, in the case of non-coordinated programs, new peak hours are likely to be formed when electricity prices are low [27, 28].

Beside flexible loads, Plug-in Hybrid Electrical Vehicles (PHEV) are penetrating into nZEBs in recent years. Since these vehicles have batteries that can be charged at different levels by the grid and can be discharged to return the energy back to the grid (e.g., vehicle to grid capability), it is necessary to incorporate PHEV in the load management procedure [29].

In off-grid mode, the most important challenge is to maintain power quality and supply reliability by balancing of renewable energy sources (PV-systems or wind turbines), with additional controllable power generation and efficient control of energy storage(s) (typically a battery) and flexible loads in nZEB [30–32] European countries have made it compulsory to use certain amounts for the minimum share of renewable resources in nZEBs [33]. High power fluctuation of local renewable systems is the main cause of reduced voltage quality in off-grid mode nZEB which leads to decreasing lifetime of electrical devices.

Economically most feasible solution for balancing renewables is control of flexible load. Load management according to renewable systems power generation is often called as load matching. Making use of thermal storages that are already in the household can, therefore, be a useful addition to generate a more efficient off-grid system. By using flexible loads for load matching is possible to reduce the install capacitance of the battery, hence reducing the investment cost of balancing (control) system. Decreasing battery capacitance results in cost reduction of entire system. Another option for better load matching is to utilize available thermal storages and heat storage capability of nZEB. As a result, by using load matching the battery storage could be reduced up to 30%. This enables a large reduction of initial investment costs in an electrical storage system. Besides investment, operation and maintenance costs may also be reduced with optimal determination of charge/discharge state of battery energy storage inside nZEB, including PHEV.

An accurate load forecast and scheduling will have an impressive effect on cost reduction and peak shaving in both on/off-grid modes. Mathematical and heuristic optimization techniques are both used in the literature

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