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Difference between revisions of "PV-CHP"

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(Optimal Operation Planning of a Photovoltaic-Cogeneration-Battery Hybrid System)
(Optimal Operation Planning of a Photovoltaic-Cogeneration-Battery Hybrid System)
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* Mathematical formulation was done in order to minimize the cost to supply electricity.  
 
* 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 utilizedin order to fulfill thermal demand for the building.
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* 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 gas absorption chiller and boiler is determined by the maximum thermal demand.
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* 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.
 
* 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.
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====='''Conclusion'''=====
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It was seen that the cO2 emission, running cost and primary energy consumption were low compared to conventional energy cost.
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===[http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4115924 Optimal Operation Planning of a Photovoltaic-Cogeneration-Battery Hybrid System]===

Revision as of 18:53, 1 February 2015

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Contents

Improved performance of hybrid photovoltaic-trigeneration systems over photovoltaic-cogen systems including effects of battery storage

This paper presents the hybridization of CHP(Combined Heat and Power)with PV(Photovoltaic)and CCHP(Combined Cooling Heat and Power)with PV. It even explains the several advantages of using CHP+PV hybrid systems and CCHP+PV hybrid systems over conventional systems. Moreover, PV-Cogen and PV-trigen are found to be more effective at reducing emissions compared to conventional systems.

NOTES:-

Review of PV(Photovoltaic)

-In PV technology solar energy is directly converted to electricity. The efficiency is only about 6-20%.

-The PV has irregularities due to local weather conditions. Thus, PV technology is not consistent throughout the year. So, PV technology is combined with CHP unit.

Review of CHP(Combined Heat and Power)

-The CHP unit uses fuel like natural gas, bio-gas etc to generate electricity.

-The co-generation unit also produces thermal energy which is harnessed by a heat exchanger and utilized

Review of Battery Energy

-Battery is a storage device.

-Whenever excess electricity is generated by the hybrid system, it is stored in the battery and it is utilized during the time when the CHP and PV unit fails to meet the requirement.

Hybrid System(PV+CHP+battery)

-Electricity generated by the PV and Cogeneration unit is used to meet electric requirements. The waste heat is harnessed by heat exchanger to provide hot water and space heating.

-Whenever, excess electricity is generated it is stored in the batteries which is used to supply electricity when PV+CHP unit fails to meet requirements.

ADVANTAGES:

  • GHG(Green House Gas) emission reduction.
  • High efficiency as most of the waste heat is utilized for heating water, space heating etc.
  • Improved performance.
  • Higher normalized power indices.
Hybrid System(PV+CCHP+battery)

-In CHP there is still some amount of waste heat. So, in order to overcome this limitation PV-CCHP hybrid system are used.

-In CCHP, the remaining waste heat from the CHP is utilized by the system for air-conditioning(space cooling).

ADVANTAGES:

  • Substantial GHG emission reduction.
  • Very high efficiency(higher than PV+CHP hybrid system)
  • Improved performance than CHP.
  • Higher normalized power indices than CHP.

Dispatch strategy and model for hybrid photovoltaic and trigeneration power systems

This paper purposes the dispatch strategy for hybrid system PV+CCHP that accounts for electric, space cooling and space heating. The CCHP(Combined Cooling and Heat Power) system is used to reduce the waste heat produced from CHP system. This has resulted in improving the performance by 50% over PV-CHP unit. Due to intermittency of PV technology CHP unit is combined with PV. To overcome the limitations of the CHP unit, PV+CCHP hybrid system is used. This paper explains the significant improvement in performance available in PV-CCHP systems over PV-CHP system.

NOTES:-

-Electricity is generated by both PV and CHP unit but in order to improve the performance storage devices for electricity and thermal loads are connected with PV+CHP hybrid units.

  • Inverter is used to convert DC output from PV and battery to AC outputs which are compatible with loads.
  • Excess AC output produced from CHP is stored in the battery.
Parallel configuration:

In this configuration, inverter(it is used to convert DC output from PV and battery to AC outputs) and CHP unit is connected in parallel.

The advantage of using parallel configuration are:

  • Reduction of capacity of inverter and CHP unit.
  • Better supply-demand correlation.
  • Maximized CHP fuel efficiency.
  • Minimized CHP maintenance costs.
Series configuration:

In series configuration inverter and CHP are connected in series. It is easy to implement, but has several flaws,

  • Lower overall system efficiencies (due to inverter and battery losses).
  • Larger inverter size.
  • A limited control of the CHP unit.
Dispatch Strategy:
  • This strategy is used to control the system in order to meet the electric and thermal load requirements.
  • The thermal output tend to be larger than electrical output in CHP. So, this strategy tends to meet the electrical requirements first, then the thermal requirements
  • When it produces excess of power, it is stored in the battery. Moreover, if batteries is at their maximum State Of Charge(SOC), then electricity is either dumped into the ground or it is penetrated into the grid. If there is excess thermal energy it is dumped as waste gas through exhaust.

Optimal Scheduling of Hybrid CCHP and PV Operation for Shopping Complex Load

This paper purposes economic optimal operation of combined cooling heating and power (CCHP) and photovoltaic solar (PV) hybrid system. The system which is simulated consists of a CCHP system, a PV system, an auxiliary boiler, an absorption chiller, a heat storage tank, and utility grids. The advantage of using CCHP, compared with conventional generation, is that it utilizes the waste heat to satisfy the thermal demand. The favorable operation of CCHP helps to minimize the operating cost and retain their investment as early as possible. There is even no fuel consumption which helps in conserving the environment.

NOTES:-

System Description

-Energy Management System(EMS) consists of:

  • CCHP:

-CCHP system generates electricity as well as heat. Electricity is supplied to the load while heat is supplied to absorption chillers to convert it into cool air.

-It is based on the gas turbine technology. It uses natural gas as the primary source.

  • PV+Utility grid:

Whenever there is shortage of supply from the CCHP system, PV+utility grid compensate for it.

  • Heat Storage tank:

-If CCHP unit produce excessive heat than the demand then heat storage tank stores the excessive heat produced from the CCHP unit.

-It will discharge the heat when CCHP unit cannot fulfill the thermal demand.

  • Flowchart working:

-Carbon-di-oxide gas emission is calculated(using linear calculation) by considering output power, fuel cost, thermal and electrical demand, energy price to verify the quality of CO2 gas.

-After that the time will be updated to the next interval and the system will operate continuously.

Institutional scale operational symbiosis of photovoltaic and cogeneration energy systems

The GHG (Green House Gas) emissions have caused increased in carbon concentration in atmosphere. The GHG emission are caused due to combustion of fossil fuels like coal, oil and natural gas. Most of its energy is wasted while converting it into electricity. The GHG emission can be controlled by efficiently use of fossil fuels, use renewable energy resources, or by using CHP(Combined Heat and Power).

This paper mainly discusses on three design scenarios 1) single cogeneration + photovoltaic, 2) double cogeneration + photovoltaic, 3)single cogeneration + photovoltaic + storage. The paper also shows that how requirement of natural gas is lowered by above scenarios. The consumption of natural gas consumption can be improved by hybridizing solar with cogeneration.

NOTES:-

Reduction of GHG:

The GHG emission can be reduced by 2 ways:-

1.Efficient use of fossil fuels:

  • By utilizing waste heat produced from the fossil fuel. The waste heat is utilized for space heating or water heating. This is called cogeneration or CHP. Further the waste heat can also be utilized for air cooling. This is called tri-generation or CCHP.

2.Renewable energy:

  • By using photovoltaic technology which directly converts sunlight into electricity. It has limitation due to weather irregularities.

So, PV+CHP can be combined to increase the efficiency of the system and reduction of the GHG emission.

CHP system:
  • In CHP prime mover converts chemical energy into electrical energy. The maximum efficiency obtained from this is 50% and remaining is wasted in the form of heat. Using heat ex-changers this heat can be utilized for space heating and water heating. Thus, efficiency can be increased.. The electrical efficiency is 35% and thermal efficiency is 50%. Hence, there is less fuel consumption.
  • The efficiency of CHP is given by:

n=(Q+E)/Q0

where: Q:heat energy. E:Electrical energy. Q0:heat content of the fuel.

  • The base load of the system is considered to be about 300kW. During evening the peak load is increased to 600kW. The load utilized during summer and winters are also different.
  • The electrical efficiency from natural gas is between 30%-40%. In this 90% of the heat loss is utlized for hot water and air cooling.

The block diagram of the CHP system configuration scheme has been provided in the paper.

PV Technology:
  • It consists of PV panels which converts photons from sunlight directly into electrical energy.
  • The output of the PV panels is DC, but the requirement for grid and appliances is AC. So, inverter is connected to convert DC to AC in order to meet the requirement.
  • The solar panels are mounted on the roof of the hospital. The tilt angle of solar panel was kept at 10 degrees. 0.5m space was kept between the panels for maintenance purpose.
Design of PV+CHP hybrid system:

The main purpose is to increase the efficiency by utilizing most of the waste heat, in order to increase the efficiency,thermal energy consumption can be reduced by installing heat control mechanism which can be done by the CHP system. PV+CHP hybrid system is used.


Scenarios:

-Scenario 1:Single PV+CHP

  • This scenario explains how the CHP unit is capable of satisfying hospitals base load requirement.
  • PV technology does not fulfill the hospitals load requirement, so CHP unit helps to overcome the loads shortcomings. During the night-time the CHP unit helps to meet the hospitals load requirement.
  • During certain months of the year, there is excess electricity generated by PV+CHP unit. This excess electricity is fed back into the grid.
  • Scenario 1 fulfills 76% of the hospitals load requirements.


-Scenario 2:Double PV+CHP

  • In this scenario 2 CHP unit are coupled with each other. Double PV+CHP is more effective but is very costly due to high maintenance cost compared to scenario 1.
  • It fulfills 93% of the energy requirement of the load, also whatever excess electricity is generated throughout the year is fed back into the grids.
  • As there is no means to store heat energy,it does not completely fulfill the hospitals thermal requirement.


-Scenario 3:Single CHP + PV + Storage

  • In scenario 3 it overcomes the shortcoming and low performance of scenario 1 and it is not as costly as in scenario 2. This is almost similar to scenario 2.
  • The battery is used to smooth out the electrical load. But this scenario has shortcoming that it has low thermal supply made available to the hospital.


Observations:
  • It can be observed that using hybrid system helps to improve the energy performance.
  • By installing PV array helps in reducing the run time of the CHP to meet load, which in turn reduces natural gas use and green house gas emission.
  • Producing energy on site is far more efficient then producing energy at power plant which involves transmission losses of around 26%


Hybrid PV-CHP Distributed System: design aspects and realization

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.


Simulations of greenhouse gas emission reductions from low-cost hybrid solar photovoltaic and cogeneration systems for new communities

This paper focuses on reduction of GHG(Green House Gas) emission and life cycle cost by optimizing the PV-CHP system. The conventional energy can be replaced by PV-CHP hybrid systems in order to reduce green house gas emission. In this paper simulation and optimization model has been developed multiobjective genetic algorithm called Photovoltaic Tri-generation Optimization Model(PVTOM).


NOTES:-

Methodology:-
  • PVTOM helps to minimize the GHG emission and life cycle cost(capital investment, fuel cost, replacement cost).This hybrid system only emits GHG from CHP unit.
  • PVTOM requires 5 inputs to simulate and optimize PV-trigeneration.

1. Hourly solar global and diffuse irradiation.

2. Hourly ambient temperature.

3. Hourly data for household’s appliance and lighting (AL) load.

4. Hourly data for household’s domestic hot water (DHW) load.

5. Hourly data for household’s space heating (SH) load.

These inputs are used to calculate the performance of PV–CHP to meet the thermal and electrical demands.

  • CHP unit generates more thermal output than electrical. So, first electrical demands are fulfilled than thermal demands are taken into consideration. If there is excess electrical energy, it is fed into the batteries. When battery reaches its maximum state of charge it is fed into the grid or into the ground.
  • The optimizer are based on the eight variables:

1. Selection of CHP.

2. Selection of PV panel.

3. Selection of battery.

4. Number of CHP units.

5. Number of PV panels connected in series.

6. Number of PV strings connected in parallel.

7. Number of battery units connected in series.

8. Number of battery strings connected in parallel.

  • The life cycle cost of the system is mathematically expressed as the sum of the the initial capital costs, the discounted operational costs, the replacement costs and penalty.
  • The table 3 in the paper provides the optimized CHP+PV unit for data selection.


A model for optimal energy planning of a commercial building integrating solar and cogeneration systems

This paper focuses on integrating cogeneration, solar and conventional sources in order to minimizing life cycle cost (maintenance cost, fuel cost etc) to meet the energy demand(electricity, heating and cooling). The paper also proposes on optimal investment planning and optimal operating strategies of the energy systems. In conventional energy sources there is not much space for energy planning and optimization of energy.This paper proposes a linear programming model to minimize the life-cycle costs of meeting the building energy demand (power, heating, cooling) by integrating renewable and traditional energy sources.

NOTES

Cogeneration system are widely known as alternative because of their high efficiency.

PV Systems
  • Location of study has been selected and hour by hour power output of silicon crystal is noted.
  • The expected lifetime of the PV system is 20 years.
Cogeneration Technologies

Three types of cogeneration technologies:

a) MT(Micor-turbine): It converts high energy gas steam runs electrical generator. Electrical efficiency is 23%-29% and overall efficiency is 64%-74%. Its benefits are easy installation, high reliability, reduced noise and vibration.

b) ICE(Internal Combustion Engine): They have electrical efficiency between 25% to 48% and overall efficiency is between 75-85%.

c) SOFC(Solid Oxide Fuel Cells): It works on electrochemical process to exploit energy present in natural gas to produce electricity. Electrical efficiency is about 43% and overall efficiency is between 74%-85%. It has high power to heat ratio.

Mathematical Model

1. Inputs:

  • Power, Heating, Cooling demand.
  • Economic data: Capital cost, residual value, operating costs, Maintenance costs.
  • System Characteristics:

- Cogeneration Systems: Power to Heat Ratio, Fuel consumption.

- Boiler: Max min operating region and COP (Coefficient of performance).

- Grid: Price per kWh

- Solar systems: solar radiation and output per systems.

2. Variables:

  • Solar System: Number of panels installed.
  • Cogeneration,thermal and cooling systems: No. of units involved and their outputs.

3. Objective function: It is to minimize the life cycle costs of meeting the power, thermal and cooling demands.

4. Constraints: Three types of constraints-

  • Demand for power.
  • Demand for heat.
  • Demand for cooling.
Results
  • The solar and cogeneration hybrid systems are capable of reaching thermal and electrical efficiency.

Combined cooling,heating and power systems:A survey

This paper focuses on working of the CCHP system. The advantages and analyses of the components of the system are presented in this paper. Control system optimization and sizing of the system is also summarized in this paper.

NOTES

  • Power Generation Unit: Use to supply electricity to the grid. The heat is produced as the by-product. This is utilized to meet heat and cooling demand. Three types of energy can be supplied simultaneously.
  • There are 3 advantages using this system: High efficiency, Less GHG emission, high reliability.
  • By adopting absorption chiller and boiler the heat which is released as by product can be utilized for heating and cooling without using electricity.
  • In conventional SP systems,approximately two-thirds of the fuel used to generate electricity is wasted in the form of rejected heat.By introducing thermally activated technologies, the electric load for cooling is shifted to the thermal load,which can be fully or partially achieved by absorbing or adsorbing

the discard heat from the prime mover.

Conclusion

The CCHP,which can provide the cooling energy by adopting the thermally activated technology. To construct an economical and efficient CCHP system,facilities type should be determined first according to the local resources,and current and future energy market.


Modelling an off-grid integrated renewable energy system for rural electrification in India using photovoltaics and anaerobic digestion

This paper describes the deisgn optimization and techno-economic analysis of off grid hybrid systems to meet the electrical demand. It also focuses on different scenarios having different combination of electricity generation.

NOTES

  • PV+AD(Anaerobic digestion)+CHP+batteries were used for generation.
  • Several scenarios were investigated. The scenarios are:

A) PV + VRB þ DCeAC B) PV + Fuel Cell þ Electrolyser + H2 tank + DC-AC C) PV + VRB + DC-AC + AD + 1 CHP (Microturbine)

Working:

The block diagram in the paper shows the working of the the hybrid system.

It converts the sunlight into electrical energy. The output of the PV is DC. But the load requires the AC as input. In order to convert DC-AC inverter is connected. Moreover, if there is excessive energy generated is fed back to the battery. It is charged upto maximum SOC(State of Charge). If the PV is not able to fulfill the demand. CHP supplies the electrical energy. The by-product of CHP is heat. This waste heat can be utilized by for space heating or air conditioning using heat exchangers or space coolers. The controller block controls all the operation depending upon the electrical or heat depend. Moreover, if there is excessive electricity generated, it is either fed into the grid or stored in the battery which depends upon whether the system is off grid or grid connected.

Conclusions

The paper explains that scenario C has several advantages over other scenarios.


Genetic algorithm based optimization on modeling and design of hybrid renewable energy systems

This paper focuses on designing of hybrid system with solar PV as renewable source and microturbine based on genetic algorithm. System with more than one supply source has more reliability and energy security compared to system with only one energy source. This paper also focuses on sizing optimization of hybrid systems components in order to minimize cost of energy, minimizing pollutant emissions and maximizing utilization of the solar panels.

NOTES

Before performing the optimization, energy generated by each source can be calculated. This is done by mathematical modelling of each component, which requires climatic data.

Simulation
  • Block Diagram:

The bidirectional inverter is used to link AC bus and DC bus. Both the DC output from the PV panels and thee batteries are connected to the DC bus. The AC bus combines both the output of the microturbine and the load. The strategy is based on maximizing the utilization of PV systems. The energy generated by the PV panels is stored in the battery bank. If battery and PV does not satisfy the load demand, the energy will be supplied by the microturbine as a standby source. In certain cases the PV panel generates excess energy which is given to battery. When the battery gets fully charged, a dump load is used to consume excess energy. The microturbine operates only when the battery is discharged below its maximum allowable discharge level and there is no sufficient energy generated by the PV systems. This continues till the battery is recharged back. Recharging is done by rectifier which converts AC to DC. Loss of load probability is the ratio of Energy deficit to Load demand.

Energy deficit is the load demand which cannot be met by the generation or the storage element.


Control strategies and cycling demands for Li-ion storage batteries in residential micro-cogeneration systems

This paper focuses on residential microgeneration system consisting of PV, CHP and battery. The storage battery was simulated under various scenarios. The principle focus of this paper is to examine the details of the load demands placed on the battery in order to know their functionality, durability, economy and capacity.

NOTES:

Several Cases were taken into consideration:

1)Grid + battery + PV ICE ON + MID

2)Grid + CHP + battery ICE ON + MID

3)Grid + CHP + PV + battery

For all the above cases, when PV or CHP unit exceeds the load demand. It charges the battery.The battery discharges during peak periods and charge during mid-peak and off grid periods. If PV+CHP unit produces excess energy even during peak periods, then the battery can be even charged during the ON-peak period. CHP unit can provide heat to thermal load without emitting waste heat.

The flowchart in the paper is self explanatory, PV and CHP unit is used to provide energy to electrical load. The waste heat generated from the CHP is utilized by thermal loads, increasing the efficiency of the system. Moreover, whenever there is excess power generated by the PV and CHP unit is fed into the grid if its grid connected or it charges the battery if its off grid. By, including CHP with PV and battery helped to provide cost benefits.


Hybrid solar fuel cell combined heat and power systems for residential applications: Energy and exergy analyses

This paper focuses on determining system operational parameters for the design and implementation of the CHP system in a residential area. The hourly demand of the residential area is taken into consideration for component selection and sizing, and energy and exergy efficiencies of the developed system are presented. In a hybrid PVefuel cell combined heat and power (CHP) system, both electricity and heat are generated from solar energy.

NOTES:

- A solar PV system is integrated with a water electrolyzer, an ultra-capacitor bank and a fuel cell for power generation. The hourly difference in the PV output and the load demand is calculated.

-The CHP system was operated and provided the house with both electricity and cooling with a total efficiency of 52%.

-The waste heat was given to the steam generator for steam generation. The generated steam can be utilized for different purposes. It was used in absorption chillers for space cooling.

-The PV system is the main part of the electricity generation module. PV panels are connected in series and parallel combination. The PV system performance is affected by the ambient temperature. The PV cell power output is I � V and based on the non-linear characteristic.

Conclusion:

-The total efficiencies of the renewable PV+CHP are calculated. The maximum energy and exergy efficiencies of the photovoltaic system are 17% and 18.3%, respectively. The total efficiency of the PV fuel cell CHP system is based on the pattern of the availability of solar and load demand. The maximum total energy efficiency is reported as 55.7%, while the maximum total exergy efficiency is 49.0%.


Uncertainties in the design and operation of distributed energy resources: The case of micro-CHP systems

This paper focuses on how distributed energy resources will have profound impact on the electricity infrastructure functioning. The paper even focuses on residential, or micro (m) DERs. Households consume energy in the form of electricity and heat. Installing Distributed generators(DG) will have economic and environmental potentials.

NOTES:

  • The DER (Distributed Energy resources) has three sub concepts:

1) Distributed Generator of electricity(DG).

2) Distributed Energy storage.

3) Controllable energy loads.

  • DG technologies are photovoltaic systems, Wind turbines, combined heat and power and other renewable sources.
  • Benefits of using DG are: Low GHG emissions, Increased Efficiency, Reduced risk of investment.
  • By installing DG we can utilize the waste heat emitted while converting primary fuels into electricity. This waste heat is utilized by Combined Heat and power(CHP), which can be used for space cooling, water heating etc. Thus, makes more efficient use of energy and thus saving cost and minimize carbon emission.
  • DERs combined with more ICT(Information and communication technology) enables smarter power systems, more active and intelligent network management, and demand response options at the consumer level.
  • Residences with DERs can work independently of energy suppliers.
  • The electricity and the heat demands of the residences are fulfilled by several alternative supply. The CHP unit consists of a Stirling engine prime mover and auxiliary burner. The prime mover converts natural gas into electricity and heat.
  • The waste heat is supplied to the heat storage in the form of hot water, the auxiliary boiler provides additional heat. The devices which consumes heat is taken from the heat storage.
  • Heat is demanded for domestic hot water and space heating. A large heat storage is provided in order to meet the demand for space heating and domestic hot water.
  • Electricity generated can be stored in the battery. It can be supplied when energy demand is not met. The energy is stored in the battery when excess electricity is generated.
  • Simulation Inputs: Daily elctricity and heat demands for certain years have been taken into consideration.
Conclusions
  • Cost savings are higher by installing CHP then conventional sources. The cost saving is more in the colder regions.


Structure optimization of energy supply systems in tertiary sector buildings

This purpose of this project is to optimize model using mixed integer linear programming to determine the type, number and capacity of equipments in CCHP system. The objective is to minimize the annual cost of energy. This paper focuses an integrated energy-planning based on MILP to determine the optimal configuration of energy supply systems. The requirement of heating and cooling are not simultaneous as this demands are seasonal.

NOTES:

  • The input to the trigeneration are purchased electricity, sold electricity and fuel prices. The output is heat demand, electrical demand and cooling demand. It can sell electricity if its produced in surplus during off peak time.
  • In order to meet the thermal and electrical requirements of the building CHP unit is taken into use. Combining of CHP unit with the absorption chillers, the waste heat can be utilized to meet cooling load demand during summers.
  • The trigeneration is used in order to meet the electrical, domestic hot water and cooling demand. trigeneration technology is based on combining cogeneration with the absorption chillers. The cogeneration module includes thermal motor which converts the fuel into mechanical energy. It also consists of alternator which converts mechanical energy into electrical energy. Heat exchangers are used to utilize the waste heat. This waste heat are utilized by absorption chillers for cooling purpose during summers.

Energy demand

  • The cold water, hot water and electricity demand for each month has been provided in the paper. This demand can significantly affect the energy saving and economic characteristics of the CCHP.
  • Equivalent Electrical Efficiency (EEE) of the CHP is given by:

EEE=(Generated electricity)/(Consumption of the primary energy-(Cogenrated useful heat/0.9))

  • It was examined that installing of cogeneration technology was beneficial in all scenarios.


Expanding photovoltaic penetration with residential distributed generation from hybrid solar photovoltaic and combined heat and power systems

This paper mainly focuses on the potential of taking into action a distributed PV and CHP hybrid system and how it can help in order to increase PV penetration level in the U.S. The installation of such a hybridized section will reduce the energy waste and will also increase the share of Solar PV. Moreover, it also analyzes the the distribution of solar flux, heating and electrical requirements.

NOTES:

  • The PV technology is high intermittent. So, PV is hybridized with CHP system.
Technical Limitation to PV penetration in the current grid
  • The overall grid efficiency can reduce due to increased duty cycle.
  • At high PV penetration (eg>20%) the cost saved by intermittent load will increase instead of decreasing. The variation in PV power that create this problem are 1)day/night cycle 2)yearly cycle 3)fluctuating cloud condition.
Electrical and heat requirements of representative U.S. single family
  • CHP system can be used in order to meet electrical and heat demands. Moreover, CHP helps in increasing the penetration level of the PV.
  • If we observe the solar flux and electricity demand at various hot and cold region just installing PV system cannot met all the demands. It even needs to meet the thermal demands for that region.
  • When the PV system is not providing enough power the CHP system will turn on and will maintain a constant load. A CHP+PV system in hotter region can give maximum efficiency if the heat generated by the CHP unit is used for cooling( using absorption chiller) such a system is called CCHP(Combined Cooling , Heating and power). The solar flux is lowest during winters. Only for certain hours of the day the load can meet its demand through solar. For the remaining hours this demand can be fulfilled by the CHP unit. During Peak hours PV generates excess energy and that will be stored in the battery, the energy from this can be supplied when PV does not supply fulfill energy demand.
Design of Solar PV and CHP hybrid system
  • The PV+CHP system consists of 3 technologies:-

1)PV array

2)a natural gas engine generator

3)Advanced warm air heating system.

Technology Evolution of CHP units:-

0th generation:- CHP and advanced thermal comfort for variable thermal loads.(no electric loads). It cannot dump heat causing excessive warming of the house. CHP cannot operate at partial load.

1st generation:- CHP + PV and advanced thermal comfort for variable thermal loads-fixed input for generator heat dumping-load following in backup mode. PV panel converts 20% of the sunlight incident on them rest is wasted. This type of system is 84% efficient.

2nd generation:-CHP + PV and advanced thermal comfort for variable thermal loads-fixed input for generator heat dumping-load following in backup mode. In this CHP system offers 100% backup for PV.

Future generations:-It is designed to utilize greater percent of heat energy available from CHP unit. Hence,increasing the efficiency of the system. Adding a Absorption chiller to the system to utilize the CHP produce heat for cooling. Even trying to reduce the wasted energy from the sun this an be done by adding a solar thermal system.


Dynamic simulations of hybrid energy systems in load sharing application

The paper focuses on analyzing the energy, environmental and economic performance of two hybrid micro-cogeneration systems in a load sharing application. This is done in order to compare the performance of this two hybrid systems. It even explains that by introducing micro-cogeneration helps in saving energy, it is even economical feasible and better environmental performance i.e low emission of GHG (Green House Gas).

NOTES:

  • Cogeneration (CHP, Combined Heat and Power) means the combined production of electric and/or mechanical and thermal energy from a single energy source.
  • The thermal load of residential users typically occurs in the evenings and early mornings, while for commercial it occurs at day time. So single system can be used to provide thermal and cooling demand.
  • In this paper several cases are consideredto observe the performance in load sharing approach.

1)conventional case with one boiler and one chiller for each building.

2)conventional case with a common boiler and chiller in load sharing approach.

3)Ground Source Heat Pump (GSHP) systems in load sharing.

4) Hybrid system with GSHP and microcogenerator based on FC in load sharing.

5)Hybrid system with microcogenerator, GSHP and PVT collectors in load sharing.

Simulation inputs and control approach

1)Domestic Hot water demand.

2)Electric load Demand: It was considered for three type of days saturday, sunday and weekdays.

3)Equipment Capacity: It is the capacity and nominal characteristics of the main components.

4)Control strategy: Time during which heating is turned on in the house and the office.

Energy, environmental and economic analysis

In order to study above cases, energy, environmental and economic analysis are made.

The hybrid microcogeneration systems showed good improvements both in terms of energy and environmental performance. Performance can be further improved by introducing the PVT in the system.


Operational strategy and marginal costs in simple trigeneration systems

This paper analysis the operation of simple trigeneration system. The system is connected to the utility in order to supply electricity and receive excess of electricity. Moreover, thermoeconomic analysis is made depending upon production cost and the best operational strategy as a function of demand for energy services and prices of the fuel. The trigeneration also provide several advantages, energy savings, low GHG emissions and low energy cost.

NOTES

  • Combining CHP with absorption chillers can fulfill the cooling demand during summers.
  • To design an energy system, the following things need to be considered:

(i) the technologies and equipment to install.

(ii) the demands to be satisfied.

(iv) the energy prices.

(v) the optimal operation taking into account the possibility of operating the equipment at variable load.

Simple trigeneration system
  • Cogeneration system consist of prime mover which converts fuel to shaft power. The alternator is used to convert mechanical energy to electrical energy. The heat recovery unit utilizes the waste heat.
  • Trigeneration consists of cogeneration module with absorption chiller.The purpose of the trigeneration system is to attend the demand

of different energy services (electricity heating, and cooling). By using several equations the cost and efficiency of several equipments of the system is calculated.

Conclusions
  • This paper showed the characteristics of different operation modes of a trigeneration systems.
  • The cost of energy demand was reduced by optimal operation mode.


Control strategies and configurations of hybrid distributed generation systems

This paper focuses on the main topologies which can be adopted for hybrid system. It also discusses on a hybrid system which combines two different energy sources and explains the power flow for both grid connected and standalone system. It also analyzes on system design aspect and power flow control strategies.

NOTES:

  • The hybrid distributed generator system in thsi paper consists of the CHP unit.

CHP unit: It consists of internal combustion engine(ICE) which is fueled by natural gas, induction machine(IM), Heat exchanger(TRU), gas heat generator group(GHG).

IM: It generates electric power load.

ICE: It generates thermal power which is recovered by TRU, which is stored into the water heat storage unit.

  • PV unit: It consists of three arrays each generating electrical power of 3kW. The output of the each PV array is followed but the DC-DC converter and it is connected to a common DC bus which is followed by DC-AC converter.
  • Battery bank: The batteries are connected to the Dc bus through a bi-directional chopper(DC-DC converter). This unit is used in order to transfer power in both direction. Normal lead acid batteries in standby condition are used with a constant floating voltage of 2.25V per cell.
  • Control and energy management: There are three different control structure involved:

1) Centralized control

2) Distributed control

3) Hybrid centralized and distributed control: It has been adopted for PV-CHP hybrid system. The two main task are:

a) It establishes the power references for PV unit CHP unit and battery bank.

b) It manages heat storage unit and battery bank power flow.

Two operation modes are possible:

Mode I: The power generated by the PV unit is transferred into the grid whereas CHP unit priority is to satisfy the thermal load demand.

Mode II: The hybrid system priority is to satisfy the electric load power and CHP full load operation till possible.

Conclusion:

This paper has proposed a high level control strategy which allows both standalone and grid connected operation mode.

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

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.

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