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Difference between revisions of "Microgrid PV-CHP-Battery: literature review"

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(Conclusion)
(Storage and management as key aspects of microgrids)
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*The development of storage technologies allows greater storage capacity of electric power in DC,and power electronics.
 
*The development of storage technologies allows greater storage capacity of electric power in DC,and power electronics.
 +
 +
===[http://www.sciencedirect.com/science/article/pii/S1359431114008941 Optimal sizing of hybrid solar micro-CHP systems for the household sector]===
 +
Caterina Brandonia, Massimiliano Renzib
 +
 +
The paper mainly focuses on the importance of optimal sizing hybrid microgeneration systems. The parameters which should be considered for sizing phase are:  energy prices,ambient conditions,energy demand,units' characteristics,electricity grid constraints. This paper also focuses on maximizing the economic and the energy savings compared to conventional generation.
 +
 +
===='''NOTES:'''====
 +
 +
* Renewable or fossil fuels are used to operate combined heat and power production, providing important results in terms of energy savings and emission reduction.
 +
 +
* Due to the intermittency of the Pv technology the integgration of solar with grid was a problem.This problem was mitigated by introduction of hybrid systems, consisting of coupling solar systems with micro-CHP units fueled by natural gas.
 +
 +
* When dealing with hybrid systems, identifying the optimal sizing of the energy conversion systems is a tough issue due to several parameters that must be taken into account in the analysis, such as electricity and fuel price, energy loads and weather conditions.
 +
 +
=====''' Energy system modeling'''=====
 +
 +
* The system was made up of PV, micro-CHP device (the technologies considered are ICE, Stirling, microturbine and fuel cell), a Thermal Energy Storage (TES), a cooling device (vapour compression chiller or water/LiBr absorption chiller)
 +
 +
* Meteorological Year database for determining the yield of Solar system depending on solar radiation and ambient conditions.
 +
 +
* The hourly values of the following quantities are used: the Direct Normal Irradiation (DNI); the global solar irradiation over a south-oriented 30degree tilted surface; the ambient temperature.
 +
 +
* The efficiency of a PV panel depends on the ambient conditions, the most influential being the available solar radiation and the solar cell temperature figures.
 +
 +
=====''' Micro-CHP modeling'''=====
 +
 +
* All the micro-CHP units were modeled on the basis of electrical efficiency and power to heat ratio.
 +
 +
* The technologies considered in this work are four: ICE, Stirling engine, microturbine and fuel cell. Table is given in paper which shows comparison for all those ways of which fuel cell technique is most efficient as it has power to heat ratio =1. But it has a drawback that is its cost.
 +
 +
* It shows the advantages of using different technologies depending on the application.
 +
 +
====='''Optimal sizing of system'''=====
 +
 +
* Electrical demand can be satisfied by the (PV),the micro-CHP unit and the electricity bought from the grid (if needed).
 +
 +
* CHP unit is used to fulfill thermal demand such as space heating, hot domestic water etc.
 +
 +
=====''' Objective function'''=====
 +
 +
 +
* The objective is to minimize annual cost derived by implementation of such a hybrid system is given by sum of annualized capital cost of all the devices and annual operating cost of them.
 +
 +
* The capital cost of each device depends on its life time and capacity recovery factor.
 +
 +
* Operating cost depends on fuel cost of running CHP unit, operating and maintenance cost of the CHP unit, Cost of purchasing electric energy from grid if needed, the revenue coming from generating electric energy from solar and CHP unit.
 +
 +
====='''Conclusion'''=====
 +
 +
* The use of hybrid system is used to minimize the operating cost, overall system efficiency and low GHG emission compared to conventional energy source.

Revision as of 18:24, 21 September 2015


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Contents

Energy management strategy for a renewable-based residential microgrid with generation and demand forecasting

Julio Pascual, Javier Barricarte, Pablo Sanchisa, Luis Marroyo.


This paper presents the management strategy for residential microgrid comprising of PV and wind turbines. By using forecasted data and correcting forecasting errors according to the SOC of the battery, the strategy manages to make a proper utilizaztion of the battery resulting in a better grid power profile.

NOTES:-

Introduction

-Microgrids include distributed generators, loads, energy storage which are controlled by one unit in order to exchange power with the grid. Addind renewable system to this can lower the cost and can provide better grid quality all around the world.

-Microgrids can be classified as either grid-connected or stand-alone. It will either have renewable generators, fossil fuel generators.

-In the field of stand-alone microgrids, when the only power sources are renewable energies, the ultimate goal is to manage the energy management system in order to keep the microgrid running and schedule different units in order to reduce the operating cost.


System description

-It consists of a grid-tied microgrid with the usual electric loads for a single-family home including a heating, ventilation and air conditioning (HVAC) system.

-PV and wind turbine are installed.

Simple moving average strategy

- Two strategies have been used: SMA(Simple moving average) and CMA(Central Moving average)

-In order to make power fluctuations smooth in power exchange with the grid low pass filter can be used.

-If the power profile changes one day to another in this case the energy balance of microgrid changes and has to be compensated by battery first. This will cause SOC of the battery to drift.

Central moving average (CMA) strategy: power forecasting

- The SMA causes lag in the grid. So, CMA is used instead of SMA. This will cause lag to disappear and there will not be any need to SOC control which will result in more better grid power profile.

Conclusion

This results in energy management strategy for a residential microgrid to obtain a smooth power profile for the energy exchange with the grid. The strategy makes use of forecasted power profiles in order to eliminate the lag in the grid power profile.


Feasibility study of renewable energy-based microgrid system in Somaliland׳s urban centers

Abdirahman Mohamed Abdilahi, Abdul Halim Mohd Yatim, Mohd Wazir Mustafa,Omar Tahseen Khalaf, Alshammari Fahad Shumran a, Faizah Mohamed Nor


This paper presents the management strategy for residential microgrid comprising of PV and wind turbines. By using forecasted data and correcting forecasting errors according to the SOC of the battery, the strategy manages to make a proper utilizaztion of the battery resulting in a better grid power profile.

NOTES:-

Introduction

-Microgrids include distributed generators, loads, energy storage which are controlled by one unit in order to exchange power with the grid. Addind renewable system to this can lower the cost and can provide better grid quality all around the world.

-Microgrids can be classified as either grid-connected or stand-alone. It will either have renewable generators, fossil fuel generators.

-In the field of stand-alone microgrids, when the only power sources are renewable energies, the ultimate goal is to manage the energy management system in order to keep the microgrid running and schedule different units in order to reduce the operating cost.


System description

-It consists of a grid-tied microgrid with the usual electric loads for a single-family home including a heating, ventilation and air conditioning (HVAC) system.

-PV and wind turbine are installed.

Simple moving average strategy

- Two strategies have been used: SMA(Simple moving average) and CMA(Central Moving average)

-In order to make power fluctuations smooth in power exchange with the grid low pass filter can be used.

-If the power profile changes one day to another in this case the energy balance of microgrid changes and has to be compensated by battery first. This will cause SOC of the battery to drift.

Central moving average (CMA) strategy: power forecasting

- The SMA causes lag in the grid. So, CMA is used instead of SMA. This will cause lag to disappear and there will not be any need to SOC control which will result in more better grid power profile.

Conclusion

This results in energy management strategy for a residential microgrid to obtain a smooth power profile for the energy exchange with the grid. The strategy makes use of forecasted power profiles in order to eliminate the lag in the grid power profile.

Hybrid PV-CHP Distributed System: design aspects and realization

M. S. Carmeli*, F. Castelli-Dezza**, G. Marchegiani***, M. Mauri**, L. Piegari*, D. Rosati*


The distributed generating system uses renewable energy, but due to the intermittency of the renewable energy they are combined with hybrid plants to combine more energy. This paper focuses on hybrid plants which uses internal combustion engine with cogeneration or tri-generation and PV technology. This paper also put light on analysing the power flow control strategies. Due to very low efficeincy of PV technology they are combined with conventional non-renewable ones to improve the performance and efficiency.

NOTES:-

There are three families for Distributed Generation System (DGS):

Standalone Systems (SAS):
  • This are used to supply to remote locations which are not connected to the main grid. in such case they usually combine one or more renewable energy sources with conventional energy sources. The hybrid system assure uninterrupted power supply even when renewable energy does not operate.


Grid connected systems (GCS):
  • They operate in only grid connected mode. They are connected with one or more renewable sources.
  • By using one or more energy sources provides higher stability of power supply.
  • In GCS very small storage is equipped, in order to contribute system transient stability.


Mixed operating mode systems (MOS).:
  • They operate in grid connection mode combined with one or more renewable sources along with storage device(Battery).
  • The battery is used to supply energy during emergency period.


Hybrid System Configuration.:
  • In this PV is combined with CHP unit. It is also equipped water heat storage.
  • CHP unit has small size battery and braking resistance which are shunt connected.
  • The shunt element have three functions.

a) They allow CHP to start even in the absence of the mains.

b) they allow to store excess energy in the standalone mode.

c)They provide transient stability to the CHP system.

If shunt unit is not connected then:

a) We obtain poor dynamic response.

b)In standalone mode, if there is demand for increase in load, it wont be able to fulfill the requirement.


Hybrid system components:

- CHP unit:

  • The natural gas, fuel for Internal Combustion Engine(ICE) to generate mechanical energy by combustion of fuel. The Induction machine connected to ICE converts mechanical energy to electrical energy.
  • Thermal recovery unit recovers thermal energy using heat exchanger. The heat generated during the process produces hot water which is stored in water heat storage. The heat storage unit has temperature sensors.


- PV unit:

  • It has different PV arrays. The output is DC which is connectedd to the common DC-bus. Chopper(DC-DC converter) is used. The DC is converted to AC(inverter).


- Battery Bank:

  • It is connected to the DC-bus. This Bi-directional Chopper. So, it can supply power in both directions, form DC bus to battery during charging of battery and from battery to DC bus during discharging.
  • There are two charging steps:

1) Constant current-Bulk condition.

2) Constant Voltage- Boost condition.


-Supervisor control unit:

It has two main tasks:

  • Controls input of PV, CHP and Battery bank.
  • Controls heat storage unit and battery power flow.

There are two operation modes:

1) Normal operation mode: In this mode the whatever power PV unit is generated is fed into the load. The CHP unit priority is to satisfy thermal demand. If CHP generates more power than required by heat demand, it stores it in battery bank.

2) Standalone operation: In this mode grid is not connected. The hybrid system gives priority to fulfill the electric demand. Advantage is this operation does not require energy storage device.

The mode changing is controlled by supervisor control unit.

Optimal Operation Planning of a Photovoltaic-Cogeneration-Battery Hybrid System

S. Bando, Member, IEEE, H. Asano, Member, IEEE, T. Tokumoto, Non-member, T. Tsukada, Non-member, and T. Ogata, Non-member

This paper proposes the modelling of optimal planning of hybrid systems and economic dispatch of the hybrid system. This paper also deals with three different objective functions: minimization of cost, reduction of CO2 emission and primary energy consumption.

NOTES:

  • There is a degradation of power quality such as voltage and frequency as the renewable energy sources is fluctuating. To achieve large penetration goal of renewable source, distributed generation is considered.
  • The battery capacity can be reduced if gas engines in the hybrid system can follow the cchange in output system of renewable energy.
Micro-grids
  • In this PV+ gas engine CHP is modeled. Electrical and thermal demand were based on combined data.
  • Schematic shown in the paper consist of three gas engines, PV, steam-absorption refrigerator, gas-absorption chiller, gas boiler, and lead acid battery.
  • Electricity is supplied by the parallel operation of gas engines, PV and battery.
  • The calculation parameters are battery capacity, pv capacity and the number of gas engines.
Mathematical formulation
  • Mathematical formulation was done in order to minimize the cost to supply electricity.
  • In the PV-CHP hybrid system exhaust heat from the gas engines is utilized in order to fulfill thermal demand for the building.
  • The capacity of gas absorption chiller and boiler is determined by the maximum thermal demand.
  • The capacity of steam absorption refrigerator is determined by the maximum gas engine capacity.
  • Several parameters such as gas engines generated efficiences and heat recovery efficiency, PV efficeincy, gas price, CO2 emission coefficient etc are taken into consideration for optimized operation planning of PV-CHP hybrid system.
Conclusion

It was seen that the cO2 emission, running cost and primary energy consumption were low compared to conventional energy cost.

Microgeneration Model in Energy Hybrid System - Cogeneration and PV Panels

J. Galvão*, S. Leitão**, S. Malheiro**, T. Gaio***

This paper proposes the development of a hybrid energy model with solar PV panels and a small CHP (combined heating and power production) system whose primary energy source is the biomass.It also presents the several rules to achieve new energy efficiency levels.

NOTES

  • The hybrid energy model consists of following processes:

1) Cogeneration process.

2) Thermal process.

3) Electrical process.

4) PV process.

  • Cogeneration system uses biomass or ICE as primary energy sources. It provides electrical as well as thermal energy.
  • Thermal process includes heating hot water, space heating etc.
  • PV solar system is also used to produce electricity.
Energy data consumption
  • Energy and thermal demand data were considered. The three main energy sources utilized are: Electrical, fuel and gas. Their energy consumption are represented in graphical form in the paper. The most energy source consumed is electricity which contributes to around 55%
  • The energy consumption for heating and cooling varies with season. The graph shows the thermal consumption during winter days.
Energy Hybrid Concept and Solar Potential
  • This system consists of several energy sources combined together. It is used to provide electricity with low cost and low emissions.
  • The solar radiation distribution data has been provided in the paper.
  • There are two large areas in co-generation system:

1) Handling/storage of biomass.

2) Heat exchangers, filtration of gas engine/ generator.

  • If PV cant fulfill the electric demand. The additional electric demand is fulfilled by the CHP unit.
Economic Analysis
  • The PV process is combined with CHP to supply electricity during peak hours. Excess energy can be stored to electrical net.
  • The hybrid system not only fulfills the energy demand but also increases the efficiency.
Conclusion
  • Efficiency is increased by combining PV with CHP unit.
  • This system is eco-friendly i.e it does not emit GHG(Green House Gas).

Rural microgrids and its potential application in Colombia

E.E. Gaona, , C.L. Trujillo , J.A. Guacaneme


NOTES

  • A microgrid can be defined as a system characterized by a set of loads, storage systems and small-scale generation sources. Power sources can generally be of various types(renewable sources like photovoltaic or wind generators,and/or generators from fossil fuels),which fulfill local requirements for heating and power generation(Cogeneration).
  • Microgrids can exchange energy i.e.it can act as generator or load.
Microgrid concept
  • A microgrid comprises a portion of the electric distribution system in a medium and low voltage.It includes a variety of Distributed Energy Resources(DER)such as distributed generators and energy storage units,and different types of end users(electric and/or thermal loads),as well as the necessary communication equipment for energy operation and management on real time.
  • A microgrid can be either DC, AC or even a high frequency AC power grid.
  • It can be interconnected to grid or can be isolated. Depending upon the operation it has different control strategies.
  • Microgird can work autonomously when there is outage of power. This mode of operation is called isolated operation.
Types of microgrids
  • Microgrid can be classified depending upon electrical characteristics. It can be AC or DC.
  • In case of AC load it is connected to inverter which ensures adequate power quality conditions.
Storage and management as key aspects of microgrids
  • In order to store AC it is necessary to convert into DC.
  • The development of storage technologies allows greater storage capacity of electric power in DC,and power electronics.

Optimal sizing of hybrid solar micro-CHP systems for the household sector

Caterina Brandonia, Massimiliano Renzib

The paper mainly focuses on the importance of optimal sizing hybrid microgeneration systems. The parameters which should be considered for sizing phase are: energy prices,ambient conditions,energy demand,units' characteristics,electricity grid constraints. This paper also focuses on maximizing the economic and the energy savings compared to conventional generation.

NOTES:

  • Renewable or fossil fuels are used to operate combined heat and power production, providing important results in terms of energy savings and emission reduction.
  • Due to the intermittency of the Pv technology the integgration of solar with grid was a problem.This problem was mitigated by introduction of hybrid systems, consisting of coupling solar systems with micro-CHP units fueled by natural gas.
  • When dealing with hybrid systems, identifying the optimal sizing of the energy conversion systems is a tough issue due to several parameters that must be taken into account in the analysis, such as electricity and fuel price, energy loads and weather conditions.
Energy system modeling
  • The system was made up of PV, micro-CHP device (the technologies considered are ICE, Stirling, microturbine and fuel cell), a Thermal Energy Storage (TES), a cooling device (vapour compression chiller or water/LiBr absorption chiller)
  • Meteorological Year database for determining the yield of Solar system depending on solar radiation and ambient conditions.
  • The hourly values of the following quantities are used: the Direct Normal Irradiation (DNI); the global solar irradiation over a south-oriented 30degree tilted surface; the ambient temperature.
  • The efficiency of a PV panel depends on the ambient conditions, the most influential being the available solar radiation and the solar cell temperature figures.
Micro-CHP modeling
  • All the micro-CHP units were modeled on the basis of electrical efficiency and power to heat ratio.
  • The technologies considered in this work are four: ICE, Stirling engine, microturbine and fuel cell. Table is given in paper which shows comparison for all those ways of which fuel cell technique is most efficient as it has power to heat ratio =1. But it has a drawback that is its cost.
  • It shows the advantages of using different technologies depending on the application.
Optimal sizing of system
  • Electrical demand can be satisfied by the (PV),the micro-CHP unit and the electricity bought from the grid (if needed).
  • CHP unit is used to fulfill thermal demand such as space heating, hot domestic water etc.
Objective function
  • The objective is to minimize annual cost derived by implementation of such a hybrid system is given by sum of annualized capital cost of all the devices and annual operating cost of them.
  • The capital cost of each device depends on its life time and capacity recovery factor.
  • Operating cost depends on fuel cost of running CHP unit, operating and maintenance cost of the CHP unit, Cost of purchasing electric energy from grid if needed, the revenue coming from generating electric energy from solar and CHP unit.
Conclusion
  • The use of hybrid system is used to minimize the operating cost, overall system efficiency and low GHG emission compared to conventional energy source.