How to supply a poultry farm with an off-grid renewable microgrid
Cattle raising installations are often located in remote areas where the electrical grid is weak, it has low capacity or there is no access to the grid. In the present article we want to share with our readers the experience of Norvento’s team when implementing an off-grid renewable supply system.
Context of the Project
The farm in question produces free-range and ecological eggs. Its installations are located in an environmental protected area where there are important restrictions to develop certain infrastructures. Due to the remote location of the farm, there are no nearby electrical distribution lines to access the grid. Moreover, an electric supply point is not a feasible option because of its high cost and large proceedings.
Given the problem, the client former option was an off-grid diesel genset that worked 24/7. This technology entails high fuel and maintenance costs, so, the client contacted Norvento’s team to study the implementation of an energy system to reduce costs and increase the sustainability of the installation. Ideally, they wanted a renewable energy system.
Previous assessment of the installation
In a first visit to the farm, our engineers inspected and made an inventory of the existing electrical installations. They also installed a power quality analyser to determine the voltage and frequency range of the genset and analyse the client’s consumption.
The results of the quality analysis showed high voltage and frequency deviations in electrical transients produced by the limitations of an old, unstable genset that did not operate in peak conditions. Such deviations could cause early damage of the consumption elements or produce outages.
The largest consumption of the installation is a monitored ventilation system that works 24/7 to keep the premises where the animals live at a constant temperature range. Likewise, the egg process and packing system also uses the energy generated by the genset. The following consumption data was obtained from the assessment:
Image 1 – Demand data obtained from the assessment
After a comparison of different possible solutions in a preliminary feasibility analysis of the project, our proposal was to complement the diesel genset with a PV generation system, an energy storage system, a back-up system, and an energy management system. So, the installation will become an off-grid renewable microgrid.
Qualitatively, the new system provides the client with high-quality energy, considering voltage and frequency stability and reduction of harmonic and sub-harmonic distortion. Also, the reliability of the system is increased thanks to the redundancy of components and the limitation of the genset operation and wear.
Image 2 – Diagram of the proposed solution: off-grid microgrid made up of PV solar, energy storage batteries, back-up genset and Norvento’s Gridmaster Converter as the microgrid’s management system.
In installations of this size, photovoltaics is the most cost-competitive energy source. This fact, together with the possible environmentally regulations of the area that may restrict a wind power installation and the availability of a suitable oriented rooftop make us choose a coplanar PV installation.
Moreover, the existing genset was kept as back-up system, so a perfect operation is guaranteed in case of no PV production and no charge in the batteries. This genset would operate in backup mode just few hours a day, reducing the fuel consumption to the minimum in relation to the produced electrical energy. The decrease of the fuel costs and hours of operation of the genset will reduce its maintenance and increase its lifespan.
An intermittent energy supply source must be always complemented with an energy storage system. In this case, Lithium-ion batteries. The storage system is basic as it must immediately balance the renewable supply and demand of the farm. In case of energy surplus, the system stores it, so it can be used in periods when there is more demand than supply.
The installation of a power converter in the system is necessary to incorporate the batteries. It will adapt the direct current of the batteries to the alternating current of the microgrid and supply the necessary power to keep the supply-demand balance. Power converters are not always compatible with off-grid microgrids, as they must be able to constantly keep that balance. Also, they are not always compatible with a specific set of batteries as they must be able to correctly communicate with its management system, usually known as Battery Management System or BMS.
Even though at Norvento we work with different suppliers of converters, this time we used our own converter: Norvento Gridmaster Converter. It perfectly fits in with this installation as it can manage an off-grid microgrid, it has been prepared to work in a difficult atmosphere as the one at a farm and has the power required for the installation: 50kW.
The microgrid controller must guarantee that the different elements are coordinated to supply quality energy and that the safety operation of the microgrid is never jeopardized. It operates autonomously, without human intervention.
So, the controller monitors the suitable voltage and frequency, the energy available in the batteries and if the demand is met. It takes decisions to start and stop the PV system and the genset to keep the grid parameters. It also distributes loads between the generation elements and the batteries to provide the client with the optimal operation, minimize the fuel consumption and guarantee the quality of the energy supply.
Therefore, the microgrid controller communicates with all the elements and receives the data from each of them. It processes the information and returns operational instructions. Norvento Gridmaster Converter incorporates a microgrid controller able to carry out all these tasks. Moreover, it remotely monitors and manages the installation thanks to its IoT connection. So, the client or the maintenance team can access the information at any time to check the state of the system.
Image 3 – Electrical and communication tests of a Norvento Gridmaster Converter at the Technology Lab of the Norvento Enerxía Innovation Centre
Sizing the installation
Once the solution has been qualitatively defined, Norvento’s team carried out an energy flow model considering both: demand and supply. It allows us to determine the perfect size of each element of the installation. The following image shows the energy flow of a given week.
Image 4 – Energy supply and demand simulation during a summer week
In the case of the PV installation, a detailed study of the production was carried out using meteorological databases. The study shown an average horizontal solar irradiation of 1,395kWh/m2 a year. Additionally, given the importance of the PV installation in an off-grid system, a specific software was used to conduct a shading analysis, so the PV panels could be installed in the best area to increase their production. The result of the study was a 35kWp PV installation, with an estimated annual net energy production of 1,160kWh/kWp.
Image 5 – Norvento’s O&M staff installing the PV system
The model of the installation indicated that a 45kWh Lithium-ion battery system with a 90% depth of discharge would be the optimal energy storage system. The system has 95% charge-discharge efficiency.
Benefits for the client
The resulting installation can supply renewable energy to meet around 76% of the yearly energy demand of the farm. The genset will meet the other 24% of the energy demand, proportionally reducing its O&M costs. It will provide the client with financial, environmental, and operational benefits.
Financially, and considering both, the operational cost reduction and the initial investment in the new installation, the estimated energy cost (or LCOE) will be reduced from 458€/MWh to 253€/MWh. The client will recoup the initial investment in 4.3 years.
Image 5 – % of energy supplied by the microgrid and by the genset
Environmentally, we calculate an emission reduction from 12.8 tons of CO2 a year to 3.2 tons of CO2 a year. Moreover, NOx and SO2 emissions will also be reduced, avoiding pollution near the animals.
From the operational point of view of the farm, now the installation is more reliable, the consumption equipment is more protected, and the client can remotely monitor the installation using a mobile phone app.
Solutions as the one described in this article show how microgrids can be a compact and reliable solution for installations with no access to the grid or with weak grids, as they guarantee the optimal supply of renewable energy and a high quality energy supply.
Article published in Energy News