Microgrid

 

Definitio​ns of microgrid

Source: Microgrid Institute

A microgrid is a small energy system capable of balancing captive supply and demand resources to maintain stable service within a defined boundary.

Microgrids can be described by one of four categories:

  • Off-grid microgrids including islands, remote sites, and other microgrid systems not connected to a local utility network.
  • Utility-integrated campus microgrids that are fully interconnected with a local utility grid, but can also maintain some level of service in isolation from the grid, such as during a utility outage. Typical examples serve university and corporate campuses, prisons, and military bases.
  • Community microgrids that are integrated into utility networks. Such microgrids serve multiple customers or services within a community, generally to provide resilient power for vital community assets.
  • Nanogrids that serve single buildings or assets, such as commercial, industrial, or residential facilities, or dedicated systems, such as water treatment and pumping stations.

Microgrids combine local energy assets, resources, and technologies into a system that's designed to satisfy the host's requirements -- which can include factors as basic as electrification, and as complex as integrating variable DERs in a balanced net-zero system. 

What all microgrids share in common, however, is the need to optimize both energy usage and generation to achieve customer goals for resilience, reliability, and sustainability. 

Microgrid projects are driven by factors that can be very different from one deployment to another. Some key drivers include:

  • Need for electrification in remote locations and developing countries
  • Customer need for more reliable, resilient, and sustainable service
  • Grid security and survivability concerns
  • Utility needs for grid optimization, investment deferral, congestion relief, and ancillary services
  • Demand for lower-cost energy supplies than are locally available (especially at remote sites, such as islands, military or mineral/resource installations, and isolated communities relying on expensive, high-polluting fuels)
  • Environmental, efficiency, and renewable energy benefits

In many areas, however, microgrids face challenges and uncertainties across a range of issues -- including:

  • Government policy, regulation,
  • Utility tariffs, contracting,
  • Financing, risk management
  • Interconnection, interoperability
  • Resource planning,
  • System operations
  • Technology and
  • Fuel supply trends

Fully grid-tied systems that can't operate in island mode aren't microgrids, but instead are defined as grid-tied distributed generation.

Resilient community microgrids represent a creditworthy customer for accessing low-cost financing

At the gate

  • The microgrid is connected to the main grid 
  • There would be metering.
  • There would be an isolation switch to cut off connection if the mains voltage drops. 
  • The microgrid can operate for a while as an island grid.

The microg​rid co-op.

  • Owns or leases the poles, holes and wires.
  • Runs the microgrid. A contractor would probably do this remotely..
  • Buys power from PV and batteries on the microgrid.
  • Sells power to customers on the microgrid
  • Buys and sells power from and to the main grid.
  • Sets the buy and sell prices according to availability.
  • Invoices customers and pays generators.
  • Owns PV cells, batteries, and voltage stabilising devices, etc. as needed. These can be installed on public or private buildings or stand alone.
  • Sells, leases, and advises on energy saving devices, lighting, whitegoods, batteries, PV cells, etc.

E​ach building

  • Owns a smart meter and computer that buys and sells power according to price and availability.  The computer would cut off non-essential power use in times of shortages/high prices. It would buy electricity  when cheap, to store in the battery.

  • May own, lease, or host, a PV system.

  • May own or lease or host a battery or other storage device. This battery could be switched to community or private use.

  • Would have a plug for an electric car. The battery in the car would act as extra storage supplying power when expensive, and charging when cheap.

 

Smart grid

A microgrid is also a smart or intelligent grid.

An “intelligent” electricity grid has a minimal amount of waste and a highly efficient use of power. It is an electricity network that uses distributed energy resources and advanced communication and control technologies to deliver electricity more cost-effectively, with lower greenhouse intensity and in response to consumer needs.

Advanced types of control and management technologies for the electricity grid can also make it run more efficiently overall. These include things like advanced control systems and smart electricity meters that show real-time use and costs and can respond to remote communication and dynamic electricity pricing. 

 igrid.net.au/

 

The tec​hnology

Technologies available to make microgrids work:

  • Gas or diesel cogeneration / CHP
  • Fuel cells and microturbines
  • Photovoltaic (PV) modules
  • Wind, biomass, small hydro
  • Storage capacity
  • Energy management and automation systems

Safe islanding: Industry-standard (IEEE 1547) interconnection to keep PV operating during outages.

Microgrid control systems manage supply and demand in real time to maintain balanced and stable operation

 

Power consumption on a microgrid

The average car drives 38 KM/day requiring 9 kWh/day.

A 1 KW PV cell generates about 4 KWh/day.

So a car would need a 2.25kWh rooftop PV.
An average house with 1-2 adults and uses about 16 kWh/D.

A house with 2 cars, will need 18 kWh/day for cars, and 16 kWh/D for the house. Total = 33 kWh/D. 

So without losses, you would need an 8 KW PV system.

Microgrid - car plugged into home

The standard Tesla has a battery capacity of 60 kWh. 

With normal driving we use about 10 kWh during the day and return home with 50 kWh in the battery. For the evening we will need about 5 kWh to run the home.

We can easily run the house with this during the most expensive part of the day, then recharge during the night when power is cheap.

If there were 2 electric cars in a household, they could run the house and transport for 3.5 days.

The difficult part is charging the car with the PV cells during the day. Batteries are expensive.

EV and the grid

If everyone had an electric car, then our electricity consumption would be about double. If trucks and busses etc were electric also, our consumption would be more than double.

If most buildings generated and used their own electricity, then there would be no need to increase the size of our grid. It is probably about the right size now.

The average Australian car drives 14,000 KM/y and that will need about 3,000 kWh/y.

When battery prices drop, it will be possible to generate much of this with rooftop solar. Some work places, parking lots, etc. will install rooftop solar for charging cars during the day.

With so many variables, it is very difficult for power companies or governments to predict the power and grid requirements in the future.

TYPICAL ELECTRICITY USE

Households with 1-2 residents use about 16 kWh/D

Households with 3-4 residents use about 23 kWh/D
Households with 5 or more residents use at least 30 kWh/D.

Further, residents of freestanding houses tend to use more electricity than residents of semi-detached dwellings and flats, .

  Source: IPART

Examples of microgrids

Isle of Eigg - Scotland

The microgrid project was highly successful at integrating multiple renewable energy sources into an island-wide community system, and reducing diesel generator use:

110 kW of hydro power with one large 100 kW generator and two small generators.
24 kW from four wind turbines
32 kW of PV.

The Sendai Microgrid - Japan

the project achieved microgrid superstardom because of its excellent performance during the 2011 earthquake and tsunami. Following a service loss of a few hours, its engine generators were started and the microgrid supplied the teaching hospital of Tohuku Fukushi University, on whose campus it is located, with both power and heat for the duration of the two-day blackout.

Huatacondo - Chile

The University of Chile has developed Chile’s first microgrid project in a remote Andes Mountains community of 150 residents (mostly miners and their families) called Huatacondo.  

The microgrid includes a 150 kW diesel generator, 22 kW tracking solar PV system, a 3 kW wind turbine, a 170 kWh battery, and an energy management system. The energy management system provides online set‐points for generation units while minimizing operating costs, taking into account renewable resource forecast, load, solar tracking, and water consumption.

 

Hydro hut, Isle of Eigg.

 A 3 kW wind turbine

Hartley Bay - Canada

Hartley Bay in British Columbia, Canada is a remote coastal village only accessible by air or water. The Gitga’at native community of 170 members operates a remote microgrid.

UCSD - USA

The UCSD microgrid project supplies electricity, heating, and cooling for 450 hectare campus with a daily population of 45,000.

It consists of two 13.5 MW gas turbines, one 3 MW steam turbine, and a 1.2 MW solar-cell installation that together supply 85% of campus electricity needs, 95% of its heating, and 95% of its cooling.

Bornholm Island - Denmark

The island represents roughly 1% of Denmark’s population and electricity load. The OSTKRAFT Company is the utility on the island serving around 28,000 customers. The peak load on Bornholm island is around 63 MW, and annual electricity consumption in 2007 was 262 GWh. Wind power accounted for 30.2% of generation in 2007, which an above average wind penetration rate in Denmark.

UCSD Solar Panels provide shade in the car park

Kythnos Island - Greece

The PV Arrays at the Central Station
Kythnos Island is located in the Aegean Sea, close to Athens. The Kythnos Island Project was funded by the European FP 5 Microgrids program, the objective of which was to test centralized and decentralized control strategies for islanding.

It is a small village scale autonomous microgrid, composed of a 3-phase low-voltage network, solar PV generation, battery storage, and a backup generator. The grid is composed of overhead power lines and a communication cable running in parallel to serve monitoring and control requirements.

Hangzhou Dianzi University - China

Hangzhou Dianzi University is located in Hangzhou city, at the southern end of the Grand Canal of China which runs to Beijing.

Located on the university campus, the system is powered mainly by PV (120kW) and complemented with a small diesel generator (120kW) and fuel cells. The PV system consists of 728 solar panels, totaling up to an area of 946m2. Thus  it is the world’s first microgrid to achieve a 50% PV penetration rate.

PV Panels at Hangzhou Dianzi University

Intelligent Research cluster

In 2008, the Intelligent Grid Research Cluster (iGrid) was established. The iGrid Cluster is an Australian collaborative research venture between the five universities, supported by the CSIRO Energy Transformed Flagship. The purpose of the iGrid Research Cluster is to deliver a future vision for an electricity network in Australia.

Key conclusions

The key conclusions of the Cluster research are:

Decentralised energy has the potential to defer or reduce expenditure on transmission and distribution networks. Peak demand growth is one of the major drivers of network investment. Around one-third of the network investment projected to occur in Australia between 2010 and 2015, or $15 billion, is considered potentially avoidable if growth in demand is eliminated through a range of initiatives including principally decentralised energy measures (Section 2).

Decentralised energy is a viable option for delivering significant cuts in carbon emissions and costs while securely and reliably meeting customer energy needs (Section 3).

There is a high level of acceptance among energy (residential and commercial) consumers and the network of energy stakeholders that „intelligent grid‟ solutions represent a genuine alternative to a centralised grid supply (Section 4)

Distributed generation (DG) can provide benefits for both utilities and consumers. DG can reduce power loss, improve voltage profiles and reduce transmission and distribution costs if sited and sized appropriately (Sections 5, 6 and 7). 

The analysis of detailed monitoring of low emissions households demonstrates the effectiveness of household energy efficiency technologies such as insulation, solar hot water, solar PV systems. It shows how much energy and carbon emissions they save, as well as the payback period (Section 8). 

Source

 

Project 1 Control methodologies of distributed generation University of Queensland

Project 2 Market and economic modelling University of Queensland

Project 3 Optimal siting and dispatch of distributed generators Queensland University of Technology and Curtin University

Project 4 Institutional barriers, stakeholder engagement and economic modelling University of Technology, Sydney

Project 5 Intelligent grid social impact   Curtin University

Project 6 The intelligent grid in a new housing complex University of South Australia 

Project 7 Operational control and energy management Queensland University of Technology 

Housing developments in Aust

 Lochiel Park Green Village

, a master planned community that seeks to demonstrate that urban, medium density housing developments can have sustainable living as their core principle. The 106-dwelling development has installed solar PV cells, recycled water systems, gas-boosted solar hot water systems and systems have a minimum 7.5 star thermal performance rating. It also features energy-efficient lighting and appliances, a load management system to control peak demand, energy and water use feedback monitors, rainwater water harvesting, and the recycling of stormwater for toilet flushing.   Website

Currumbin Eco Village

The Ecovillage at Currumbin is an international award winning sustainable community located in south-east Queensland, Australia. The 270 acre site is set the hinterland, 7 minutes from the beautiful Currumbin Beach on the Gold Coast.
The community is the most awarded estate in Australia with over 33 accolades, including “The World’s Best Environmental Development” (FIABCI Prix D’Excellence Award 2008).

 

Suppliers of microgrid equipment

nrg.com

Tridium:  www.tridium.com

Engage network solutions: www.engagenet.com

Sutron:  www.sutron.com

Encorp: www.encorp.com

 Invensys Energy Solutions: www.ies.invensys.com

Wonderware: www.wonderware.com/home.htm

Silicon Energy: www.siliconenergy.com

Lockheed Martin: www.lockheedmartin.com.au

Source: 

 

References:

Energy management and operational ...