Energy Management System Optimizing PV Storage via Loss Comparison

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Solution Overview

Problem

The integration of photovoltaic power generation facilities into energy systems poses challenges due to reverse power flow, voltage increases, and inefficiencies in energy storage, particularly when the capacity of energy storage facilities like batteries and electric water heaters is insufficient to handle the generated power, leading to suppressed power generation and reduced energy efficiency.

Innovation Solution

An energy management system that includes a battery and an electric water heater as energy storage facilities, controlled by a unit that prioritizes energy storage based on loss comparison and predicts voltage distribution to optimize energy usage, allowing for coordinated energy storage and consumption across multiple consumers to maximize the consumable photovoltaic power generation amount.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If thermal storage operation is performed during nighttime to store hot water, then power demand is increased and reverse power flow is reduced, but energy efficiency is reduced due to heat radiation loss during daytime storage

Engineering Contradiction:
Improveheat radiation lossVSAvoidpower generation efficiency
Core Design Contradiction:
Loss of energyVSProductivity

Solution Approach 1:

The system dynamically adjusts the thermal storage operation timing based on predicted photovoltaic power generation amounts. When PV generation is predicted to be high, the system performs thermal storage during daytime instead of nighttime, making the storage operation flexible rather than fixed to traditional nighttime hours.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The system changes the operational parameters of the electric water heater based on real-time conditions. By monitoring PV power generation amounts and predicting future generation, the system adjusts when thermal storage occurs, transforming the fixed nighttime operation into a variable timing operation that optimizes energy efficiency.

Inventive Principle:
Principle #35Parameter changes

2Productivity

If battery charging is performed during daytime when PV power generation is high, then photovoltaic power consumption is increased, but charging loss reduces overall energy efficiency

Engineering Contradiction:
Improvephotovoltaic power consumptionVSAvoidcharging loss
Core Design Contradiction:
ProductivityVSLoss of energy

Solution Approach 1:

The system continuously monitors PV power generation amounts, battery state of charge, and thermal storage status to make real-time decisions. This feedback mechanism allows the system to compare charging loss versus heat radiation loss and adjust operations accordingly, rather than following a fixed charging schedule.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The battery charging operation is made dynamic by adjusting charging timing and amount based on predicted PV generation and current system state. The system can shift charging to periods when PV generation is high and losses are minimized, rather than charging at fixed intervals.

Inventive Principle:
Principle #15Dynamics

3Productivity

If energy storage facility capacity is increased to handle all PV power generation, then photovoltaic power generation efficiency is improved, but device complexity and initial cost increase

Engineering Contradiction:
Improvephotovoltaic power generation efficiencyVSAvoidenergy storage facility capacity
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The system combines battery charging and electric water heater thermal storage operations into a coordinated energy storage system. By merging these two facilities and managing them together, the system achieves better overall PV power utilization without requiring either facility to be oversized.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The energy management system provides multiple functions using the same infrastructure: it manages both battery charging and thermal storage, performs PV power prediction, monitors system state, and optimizes operations. This multi-functionality reduces the need for separate dedicated systems for each function.

Inventive Principle:
Principle #6Universality (Multi-functionality)

4Productivity

If thermal storage operation timing is adjusted to match high PV power generation periods, then photovoltaic power consumption is increased, but power demand increases causing voltage rise in distribution system

Engineering Contradiction:
Improvephotovoltaic power consumptionVSAvoidvoltage rise
Core Design Contradiction:
ProductivityVSObject-affected harmful factors

Solution Approach 1:

The system monitors distribution voltage levels in real-time and uses this feedback to adjust thermal storage and battery charging operations. When voltage rise is detected, the system reduces or pauses storage operations to prevent exacerbating the voltage issue, while still maximizing PV consumption within safe operating limits.

Inventive Principle:
Principle #23Feedback

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This system reduces the impact on the power system, increases photovoltaic power generation efficiency, and enables high-efficiency, low-carbon energy consumption by optimizing the operation of energy storage facilities and coordinating energy use among consumers.

Implementation Method 1

a battery and an electric water heater as energy storage facilities

Methodology Applied
Scientific EffectBattery (electricity): Battery (electricity)

Implementation Method 2

an electric water heater is operated such that a hot water is stored in a hot water storage tank by using cheaper electricity

Methodology Applied
Scientific EffectJoule heating: Joule Heating

Implementation Method 3

photovoltaic power generation facilities, a battery and an electric water heater

Methodology Applied
Scientific EffectPhotovoltaic effect: Photovoltaic Effect

Data Source

PatentEP2375528B1Energy management system, energy management apparatus, and energy management method
Publication Date: 2018.04.25 HITACHI LTD
  • EP2375528B1 patent drawingFigure 1
  • EP2375528B1 patent drawingFigure 2
  • EP2375528B1 patent drawingFigure 3~4

AI summary

An energy management system (120) includes an equipment data management unit (134) which manages charging/discharging loss of a battery (112) and heat radiation loss of an electric water heater (113). The equipment data management unit (134) causes a control unit (121) to perform control to give priority based on the comparison to the energy storage facility more reducing loss and store energy therein. The energy management system (120) includes a system operation calculation unit (51) which predicts a voltage distribution of the next day of a distribution system or a demand-and-supply balance amount of the entire system by state monitoring data of a power system. The system operation calculation unit (51) calculates a demand amount increasing target value necessary for avoiding a photovoltaic power generation amount suppression on a consumer end by the voltage distribution of the next day of the distribution system or the demand-and-supply balance amount, and controls the energy storage facilities so as to satisfy the demand amount increasing target value on the consumer end. Further, the energy storage facilities of other consumers can consume the photovoltaic power generation amount unable to be consumed by one consumer due to capacity shortage of the energy storage facilities.