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Virtual Battery Introduction

Charles Grunewald's picture
Pricipal Engineer (retired) Blattner energy

Retired from position as head of Electrical Sector at Blattner Energy Avon, MN  a position I was recruited to develop and head as they transitioned from a 100 year civil contractor to now largest...

  • Member since 2012
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Goal: Reduce millions of tons CO2 while storing massive amounts of renewable sourced thermal energy by displaced fossil fuel water and space heating with wind energy plus  providing 1,000s of new jobs.  The virtual battery concept  will reduce renewable generation curtailments; enhance grid reliability and provide virtual battery storage at end use customers while providing up to a 50% economic and energy stored boost to any regional battery installations.


A paradigm shift to actually use renewable energy  on a real time matching basis

There are 20 plus environmental focused Non-profit groups in Minnesota doing good work promoting renewable energy  for a reduction in greenhouse gas emissions.  Their grants and funding tend to focus on individual pieces of a renewable energy future.  There is less attention on STEM based solution matrixes for the real time use of renewable generation quantifiable in tons of CO2 and $/ton greenhouse gas (GHG) reduction.  There is an ”academic vigor” alternative to the “social mission”  climate protests by thousands.  There is a waiting opportunity for supporting  STEM based work and advocating for direct electrification of fossil fuel thermal use in buildings and processing with real time balanced use of renewable energy.   

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Technology is available to demonstrate dynamically balanced (DB)  delivery of new wind generation to the water and space heating loads currently using fossil fuel.    Water, space heating and ag processing are a huge new MN market for MN wind at an energy floor price value linked to the displaced fossil fuel plus the value placed on the tons of CO2 reduction incneitves.  Off the shelf technologies with 40 years of application history can be incorporated in the complete energy delivery system matrix from generation to customer end use. 


75% of the annual wind generated energy is coincident with the 6000 hour long MN space heating season.  For the balance of the year there is still adequate wind energy for much of water heat charging plus complimenting solar energy for air conditioning (AC) and ice storage.  Wind energy generation has a lower coincidence with annual summer electric peak.  Per Midwest Independent System Operator ( MISO) wind generation still provides  a summer peak contribution of 15% for each nameplate megawatt (MW) unit of new wind.   

 Actual modeling of annual 8760 hours of locational based wind generation with corresponding locational based ambient temperatures for space heating requirement and daily water heating use identified   75+% of annual wind output  could be matched in real time to actual space and water heating needs. The agile model needs update to reflect today’s higher wind capacity factor with new low wind blade technology!  While summer electric use conservation is critical an irony is that during the Northern US  heating season conserved electric kilowatt hours (kWhs) are just offset by an equal Btu increase in  fossil fuel space heating.    Great new business growth for the gas and oil industry!

Each gas water heater emits over 1+ tons of CO2/year and in Northern US space heat emits 10+ tons/year per home.  The CO2 emission per million Btu fuel consumed for each of the fossil fuels is respectively Nat  gas 117 lbs. (ignoring nasty methane),  Propane 140 lbs. and Fuel oil 160 lbs.  If just 5% or so of Minnesota homes had dynamic balanced  wind energy for annual space heating there would be a million ton per year reduction in CO2.   Minnesota fixed point residential and commercial use of natural gas, propane and fuel oil is about  370 trillion Btu, primarily for water and space heating.  The resultant CO2 emissions for just MN are about 22,000,000 tons CO2 reduction.

The fuel displacing storage and interruptible (SI) loads include water heating, thermal storage space heating (using below slab heat or ceramic bricks) and interruptible electric space heating such as a cold climate heat pump with a dual fuel alternate source for extremely cold days. The dual fuel is also for very limited use only when renewable generation not available or electric is interrupted.  The SI loads have low cost on $/ KW and $/kWh stored basis for storing renewable energy at the end use customer where the storage investments is already paid for.  The SI load storage equipment, unlike batteries do not degrade as to KW input, cycles of activation and stored energy.  There are millions of lineal feet of MN installed hydronic below slab heat tube in place, much of which is heated with gas.


The Dynamic Balance (DB) technology has since 2001 development been presented to energy companies including Hawaii Electric, a load management manufacture and in 2008 to a large G&T Coop with past power point copy available. The opportunity needing more pilot promotion experience is the complete “continuous Dynamic Balance (DB) of new renewable generation with new fuel displacing thermal storage and interruptible (SI) loads”.  The DB is for carbon conservation, transmission ancillary services and delivery system reliability support with associated increase in renewable penetration to serve new electrified fossil fuel thermal uses.  

The DB of renewable generation with new fossil fuel displacing loads will provide renewable generation a new CO2 reducing market .  The DB of wind to displace fossil fuels also enhances transmission reliability while redirecting future otherwise wasted over installation of wind and solar generation.  Future over installation of wind and solar is addressed in the Minnesota Potential Analysis (SPA) report. See .

Rhetorical question is why energy storage?  The answer is “because of rapid volatile generation output  changes  with wind speed, passing clouds for solar or when fast ramping needed for change in utility load”.  If there is little or no volatile generation  during darkness and/or low wind periods the energy storage need is also reduced or eliminated.   If we interrupt the balanced delivery we have a forecast based predicable increase of virtual energy available to the grid.  The energy released by interruption of SI loads is then available for serving firm load, contingency support during loss of generation or sale by the distribution utility / aggregators of customer SI load energy storage.  The virtual energy released to grid needs by interrupting SI loads can be momentary or during extended high wind periods be a day or more for thermal storage while the electrified dual fuel systems can be interrupted extended periods until a polar vortex passes.  Battery energy storage typically targets only a 4 hour storage which is also the minimum storage requirement provision in FERC 841 criteria .

The functional diagram of dynamic balancing also provides  grid operators  a dashboard display of MW being balanced , the residual  megawatt hours stored and remanding time duration of residual  thermal energy storage in water and space heat.  Continuous Dynamic Balance of Generation and Load is taught in US patent US9715261B2.

The multi-level T2 thermostats on SI loads can be cycle speed activated to the higher temp which engages  the desired  locational based commanded MW of aggregated customer SI loads at their full nameplate load rating for a predicable energy storing load response.  The response duration will be until the energy storing need passed or new SI load temp reached.  The magnitude and duration of storage response will be highly  predictable as in nines (like in 99.9) reliability.  If not a highly predicable response to grid operation it cannot  be included in system operating and planning models and is not a viable alternative.


As distributed energy resources (DER) increase along with renewable penetration operation the grid operation issues increase exponentially.   Real time DB of wind to load is operation monitored and controlled for maintaining reliable grid operation unlike a DER alternative based on guessing the customers DER response to price and many other social signals.

DB technology provides grid operators a previously not available  high speed dynamic load brake which can absorb a predicable amount of excess energy on a precise time and location basis.  The Dynamic energy storage brake can be activated for T&D delivery system contingency, sudden loss of load or sudden increase in volatile generation with benefits which include following.

  • Avoid cost and operation issues with tripping or curtailing wind, solar or cycling traditional thermal and CT generation and then restoring.  Curtailments will increase exponentially as solar and wind penetration increases.
  • Energy is stored at end use customers instead of having to transport from battery locations when grid may already be congested and at limits.
  • Provide a virtual battery response when volatile generation is on line with wind blowing or sun shining.  Note, if there is little or no volatile energy generation during low wind, cloudy periods or night when sun not shining thus the initial volatility driver for energy storage is gone.
  • With thermal storage sinks in place any physical batteries supporting the grid can then float at max charge level for the respective battery technology which for lithium economic life is understood about 75 % charge.  If not having batteries float at 50% batteries to store or release energy they are able to store 50% more energy at a near 75% charge.  The desired aggregate of SI virtual thermal battery loads can be commanded on at their high thermostat level to predictably sink excess energy leaving the physical batteries at high charge so available to release 50% more energy.  Less battery deep cycling extends battery life!
  • Energy storage charge of SI loads does not degrade unlike batteries which begin to degrade day one when installed down to about 60% in 10 years of cycling .
  • There is a 50% increase in battery energy available for reliability and or predicable energy to bid in for sale or reduce purchases.  
  • Capital conservation is provided as the 50% more energy stored means huge battery economic gains for new battery installations as they can be reduced in size and cost accordingly.  


Current battery applications are heat limited as to the number, depth of charge / discharge cycles per day and cooling down before available after recharging.  Since battery round trip efficiency is 85% or so the megawatt hours of energy inefficiency goes into heating the batteries so still more energy required for the battery cooling systems.  An irony of batteries is that their stored grid energy can have carbon mix even when the renewable penetration reaches a high level of say 80%.  Currently the heat rate for Minnesota generation is about  6,000 Btu fuel per kWhr generated.   The carbon rate will be significant for years to come even though utilities are making the renewable transition goals as transmission constraints and NERC reliability mandates allow.    

Battery temperature is closely monitored less the battery owners lose their battery warranty.  Dynamic brake and Dynamic Balancing wind and thermal storage conserves the amount that batteries are exercised and reduces the heat associated life decay in life thus extending battery life.

Behind the meter customer batteries may be maintained at max storage charge for customers  emergency energy needs or time shifting for optimizing energy prices compromising  ability to predictably plan for absorb excess energy or release energy for grid operation.  DB is continuous and can provide predicable Dynamic Brake energy absorption response for grid reliability.

If a distribution utility has no batteries it can still offer a predicable virtual battery response by interrupting delivery to SI loads for virtual capacity response or T2 thermostat activation for absorbing momentary excess energy. 

Dynamic balance can also skew balance between nodes on the bulk transmission system and high speed brake activation of SI loads can temper various high voltage excursions and/or temper effect of initiation or arriving of cross county traveling waves on the transmission system.

Customer SI loads are linked to long term stable wind and solar bus bar prices which can be fixed long term like 7 to 10 plus years and with renewable energy there is no fuel adjustment clause!

Charles Grunewald's picture
Thank Charles for the Post!
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Matt Chester's picture
Matt Chester on Jun 9, 2021

Are there any particular regions or projects that are doing this virtual battery implementation in the best way, in your opinion? Who's the shining example on the hill, if there yet is one? 

Bob Meinetz's picture
Bob Meinetz on Jun 9, 2021

Charles, I admit your torrent of sales techno-babble lost me early on, but - what on Earth is "fossil fuel water"?


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