Machine Learning Techniques for the Smart Grid – Modeling of Solar Energy using AI

Networked and Embedded Systems

Professor Dr. Wilfried Elmenreich Dr. Tamer Khatib|

Overview

• Scope of this tutorial

• Meta-heuristic search algorithms

• Artificial neural networks

• Modeling of solar radiation

Modeling extraterrestrial and terrestrial solar radiation

Clear sky model

Satellite based models

Sky transmittance-based models

Ground meteorological measurement based model

ANN Based modeling of solar radiation

• Automated planning and scheduling

• Machine learning

• Natural language processing

• Perception

• Robotics

• Social intelligence

• Creativity

• Artificial general intelligence

Artificial Intelligence Areas

• Automated planning and scheduling

• Machine learning

• Natural language processing

• Perception

• Robotics

• Social intelligence

• Creativity

• Artificial general intelligence

Artificial Intelligence Techniques

• Metaheuristic search algorithms

PART I

• For optimization problems

• Etymology:

– Meta – upper level

– Heuristic – to find

– Heuristic = deterministic

– Meta-heuristic = utilizing randomization in search

• So it is “only” for search problems ?

Every engineering or design challenges can be formulated into a search

problem over a solution space

• Solution space can be particular large and multi-dimensional

– Standard optimization algorithms don’t finish in acceptable time

– Need for meta-heuristic

Meta-heuristic search algorithms

Overview on Search Techniques

• Metaheuristics = Guided random search techniques

• Metaheuristics are strategies that guide the search process

• Goal is to efficiently explore the search space to find

(near-)optimal solutions

• No single technique

• Metaheuristic algorithms are approximate and typically

non-deterministic

• Metaheuristic algorithms might fail by getting trapped in

confined and deceptive areas of the search space

• Metaheuristics are typically not problem-specific

Properties of Meta-heuristic Search

Algorithms

• Trajectory methods

– Basic Idea: Iterative improvement

– Simulated annealing (Scott Kirkpatrick, C. Daniel Gelatt and Mario P. Vecchi, 1983)

– Tabu search (Fred Glover, 1986)

– Variable neighborhood search (Mladenovic, Hansen, 1997)

Meta-heuristic Search Algorithms (1)

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• Population-based methods

– Genetic algorithm (John Holland 1975)

– Evolutionary algorithms

– Genetic programming (Fogel 1964)

– Swarm Algorithms

Meta-heuristic Search Algorithms (2)

Evolutionary Algorithm

Searching for Rules

• Simulation of target system as

playground

• Evolvable model of local behavior

(e.g., fuzzy rules, ANN)

• Define goal via fitness function (e.g.,

maximize throughput in a network)

• Run evolutionary algorithm to derive

local rules that fulfill the given goal

System model Goals (fitness function)

Simulation

Explore solutions

Evaluate & Iterate

Analyze results

System architecture

Building Self-Organizing Systems 13

Wilfried Elmenreich

6 major components: task description, simulation setup, interaction interface, evolvable decision unit, objective function, search algorithm

Agent behavior to be evolved

• Controls the agents of the SOS

• Processes inputs (from sensors) and produces output (to actuators)

• Must be evolvable – Mutation

– Recombination

• We cannot easily do this with an algorithm represented in C code…

Agent

Control System

„Agent‘s Brain“

Artificial Neural Networks

• Each neuron sums up the weighted outputs of the other connected neurons

• The output of the neuron is the result of an activation function (e.g. step, sigmoid function) applied to this sum

• Neural networks are distinguished by their connection structure

– Feed forward connections (layered)

– Recursive (Ouput neurons feed back to input layer)

– Fully meshed

Evolving Neural Networks

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Mutation

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Framework for Evolutionary Design

• FREVO (Framework for Evolutionary Design) • Modular Java tool allowing fast simulation and evolution • FREVO defines flexible components for

– Controller representation – Problem specification – Optimizer

Giving FREVO a Problem

• Basically, we need a simulation of the problem

• Interface for input/output connections to the agents – E.g. for the public goods game:

– Your input last round

– Your revenue

• Feedback from a simulation run -> fitness value

• FREVO source code and simple tutorial for a new problem at http://frevo.sourceforge.net

PART II

• Modeling of solar radiation

Application example

• Modeling of solar radiation

Modeling extraterrestrial and terrestrial solar radiation

Clear sky model

Satellite based models

Sky transmittance-based models

Ground meteorological measurement based model

ANN Based modeling of solar radiation

• Solar energy is part of the sun’s energy which falls at the earth’s surface. It

can be harnessed, to heat water or to move electrons in a solar cell.

• Solar radiation data provide information on sun’s potential in a specific

location. These data are very important for designing solar energy systems.

• Due to the high cost and installation difficulties in measuring devices, these

data aren't always available. thus, alternative prediction ways are needed.

Preface: Solar energy

How big is solar energy ?

Source: Boyle, G. 2004. Renewable Energy. OXFORD..

Modeling of extraterrestrial solar radiation • The Sun emits radiant energy in an amount that is a function of its

temperature. Blackbody model can be used to describe how much

radiation the sun emits. A blackbody is defined to be a perfect emitter as

well as a perfect absorber

• The wavelengths emitted by a blackbody depend on its temperature as

described by Planck’s law:

𝐸𝜆 =3.74×1010

λ5[𝑒14.4𝜆𝑇

−1]

Where,

Eλ is the emissive power per area (W/m2 μm),

T is the absolute temperature of the body (K),

λ is the wavelength (μm).

Modeling of extraterrestrial solar radiation • To calculate the daily extraterrestrial solar radiation on the top of the

atmosphere, the path that the earth rotates around the sun must be

considered.

• The eccentricity of the ellipse is small and the orbit is, in fact, quite nearly

circular. Therefore, the extraterrestrial solar radiation in W/m2 can be

described as,

𝐼𝑜 = 1367 ×𝑅𝑎𝑣𝑅

2

where

Rav is the mean sun-earth distance

R is the actual sun-earth distance depending on the day of the year

• After all, the daily extraterrestrial solar radiation can be given as follows,

𝐼𝑜 = 1367[1 + 0.034 cos360𝑛

365]

Modeling of terrestrial solar radiation

• Attenuation of incoming radiation is a function of the distance

that the beam has to travel through the atmosphere, which is

easily calculable, as well as factors such as dust, air pollution,

atmospheric water vapor, clouds, and turbidity

Modeling of terrestrial solar radiation

• There are many theories for modeling terrestrial solar radiation,

Clear sky model

Satellite based model

Environmental measurement based model

Ground meteorological measurement based model

Clear sky model

• Beam radiation at the surface can exceed 70% of the extraterrestrial flux

• Constant and uniform attenuation factor is assumed

• Isotropic model is assumed

Clear sky model

Satellite based models

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Sky transmittance-based models

Ground meteorological measurement based model

Ground meteorological measurement based model

Ground meteorological measurement based model

Sensitivity of data

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Model type and configuration and inputs

Number of neurons in the hidden layer

• If a low number of hidden neurons are used, under fitting may occur and

this will cause high training and generalization error while over fitting and

high variance may occur when the hidden layer consist of a large number

of hidden neurons.

• Usually the number of hidden nodes can be obtained by using some rules of

thumb. For example,

• the hidden layer’s neurons have to be somewhere between the input layer

size and the output layer size.

• the hidden layer will never require more than twice the number of the

inputs.

• the number of hidden nodes are 2/3 or (70%-90%) of the number of input

nodes.

• In addition, it has been recommended that by adding the number of the

input to the number of the output and multiply the result by (2/3), the

number of the hidden nodes can be achieved.

Modeling results using GRNN

Summary

• Artificial Intelligence algorithms are complex algorithms to handle complex problems

• Simple, deconstructable problems (given network, linear composable power flows) -> standard algorithms

• Complex problems (many variables, open questions such as network structure) -> complex algorithms

• We covered: – Evolutionary algorithms

– Artificial neural networks

– Neural network application for modeling of solar radiation

Thank you

Welcome any question

Einführung in Smart Grids 39

Wilfried Elmenreich

Further Links

• Video: 6 minute introduction to FREVO: http://youtu.be/1wTyozYGG4I

• Download FREVO (open source): http://frevo.sourceforge.net

• A. Sobe, I. Fehérvári, and W. Elmenreich. FREVO: A tool for evolving and evaluating self-organizing systems. In Proceedings of the 1st International Workshop on Evaluation for Self-Adaptive and Self-Organizing Systems, Lyon, France, September 2012.

• I. Fehervari and W. Elmenreich. Evolution as a tool to design self-organizing systems. In Self-Organizing Systems, volume LNCS 8221, pages 139–144. Springer Verlag, 2014.

• T. Khatib, A Mohamed, K Sopian. A review of solar energy modeling techniques. J. of Renewable & Sustainable Energy Reviews. 2012.16(5): 2864-2869.

• T. Khatib, A. Mohamed, K. Sopian, M. Mahmoud. Assessment of Artificial Neural Networks for Hourly Solar Radiation Prediction. J. of Photoenergy. 2012. 2012(ID 946890):1-7.