Assessment of the Carbon and Cost Savings of a Combined Diesel Generator, Solar Photovoltaic, and Flywheel Energy Storage Islanded Grid System

Abstract

The use of diesel generators to provide power for islanded grids has been the technology of choice but they generate substantial carbon emissions unless the part or all the fuel comes from a renewable source. Notwithstanding this, the engine must be sized to meet maximum demand and will operate inefficiently at part load most of the time, which is particularly bad for a synchronous constant speed engine. Given the availability of low cost solar photovoltaic (PV) systems, it is very enticing to fit a diesel generator and allow the engine to be turned off during PV generation. However, this combination will not work without some form of energy storage since it takes time for the engine to start, leading to gaps in supply and instability of the system. Lithium-ion batteries are typically considered to be the best solution to this problem because they have a high response rate, costs are lower, and they are available as products. However, they will suffer from the limited cycle and calendar life due to high cycling requirements in the application described. It is, therefore, proposed that a flywheel system could offer a lower lifetime cost alternative since only short duration bridging power storage is needed and flywheels of appropriate design can offer lower power cost than Lithium-ion battery systems. Flywheels are particularly attractive since they have a very high calendar with almost an infinite cycle life and are fully recyclable at the end of life. This research, therefore, presents an assessment of the flywheel energy storage system (FESS) as an alternative to electrochemical batteries to supplement solar PV systems backed up by diesel generators. The model of an islanded PV system combined with a diesel generator and a FESS supplying power to a residential load is implemented in MATLAB/Simulink. The results of the analysis for the cases with and without storage based on a number of different charge-discharge strategies provide evidence to support this hypothesis.

Hybrid PV System with High Speed Flywheel Energy Storage for Remote Residential Loads

“…It is proposed and will be demonstrated with supporting results that FESS would be the feasible technology for providing back-up power which leads to reduced operation of diesel engine resulting in less emissions and reduced fuel burn. The storage capacity of the flywheel technology is independent of temperature fluctuations, therefore, contrary to batteries, it would be a suitable alternative for the islanded grid system in the countries with high temperatures [9]. The application of a PV hybrid mini-grid system (PVHMS) consisting of PV system, DGen and the FESS technology for applications in small towns located in remote areas was hence studied.…”

“…HRES is considered a cost-effective solution to meet energy requirements [7] in the areas where the extension of the conventional grid is not possible or is not cost-effective. Technical assessments and performance evaluation of HRES utilizing solar PV and wind with a suitable ESS are discussed in [4,8,9]. Applications of hybrid standalone PV systems with battery storage has been widely researched as evidenced in publicly available literature, although other energy storage technologies such as pumped hydro, gravity systems and compressed air storage could offer options for the same applications.…”

Reconfigurable solar photovoltaic systems: A review

“…SPV has become the most attractive renewable source due to its high life span together with low maintenance requirements and costs. Due to its modular nature and lightweight, transportation and installation are much easier when compared to other technologies [ 7 , 8 , 9 ]. Considering these desirable features, a growth in SPV integration to the utility grid can be expected.…”

Analysis of Standby Losses and Charging Cycles in Flywheel Energy Storage Systems

“…Notwithstanding the outgassing issue, maintaining a high level of vacuum is another challenge and requires constant operation of a vacuum pump, especially for the cases when high vacuum level is maintained using gas mixtures such as SF 6 and H e [7]. However, if the requirement for the vacuum level is not too high, it can be easily maintained with the low-cost solution of hermetically sealing the flywheel containment and pumping the casing down intermittently [8]. This mechanism will reduce the wear on the pump and the loss of power due to continuous running of the pump [9].…”