By Edward C. Myers, MSChE
Project Manager, Lescure Engineers, Inc.

Family owned and operated, the Kunde Family Estate winery produces ultra-premium, estate-grown, and sustainably farmed wines in the finest traditions of the renowned Sonoma Valley. The founder, Louis Kunde, who emigrated from Germany, acquired the Wildwood Vineyards ranch with its acclaimed iron-rich, ancient red volcanic soils in 1904. In the early 1990s, the current Kunde Estate Winery and its barrel aging caves were constructed near the picturesque town of Kenwood.  Presently, twenty varietals of sustainably grown wine grapes are cultivated on 700 acres of land surrounding the winery. The Kunde Estate Winery employs classic winemaking techniques, such as cultured and native yeasts, malolactic fermentation, aging sur lies, and barrel aging with a goal of creating stylish and complex wines.

The Kunde family, like many vintners, is very interested in sustainable winemaking.  A growing concern with many vintners is the unsustainable greenhouse gas (GHG) impact of their operations.  Modern winemaking has benefitted from mechanical refrigeration for product temperature control and building climate control.  These refrigeration systems consume the majority of electricity in wineries. Electricity purchased from the local public utilities requires the combustion of natural gas, resulting in significant GHG emissions. Some wineries have installed large photovoltaic (PV) solar power arrays to reduce their utility power purchases, to reduce the GHG emissions associated with their operations.  However, energy efficiency measures can often reduce these GHG emissions at lower cost that PV arrays.   Locating and quantifying these efficiency measures requires careful study by expert practitioners; without such investigation, large potential savings may be missed.

The Kunde family wished to have their winery evaluated for energy use, to discover how much they could reduce power consumption through energy efficiency measures.  In 2007, they contracted with AIM Associates, a Petaluma architectural firm, whose principal George Beeler is a recognized expert in green building practices.  George teamed with Dr. John Rosenblum of Rosenblum Environmental Engineering and Ed Myers of Lescure Engineers, to perform an energy audit of the winery processes and main building.  These professionals are the core of the DesignSmart Group, who specialize in taking a whole systems approach to sustainable design for wineries, dairies, and other facilities. Following the audit, an engineering analysis of the performance of the winery processes and the winery building showed how the facility could be upgraded to sustainable, renewable energy at the lowest cost.

The energy audit lasted three weeks during the harvest (crush) season in August and September 2007.  Recording power instruments were attached to all the major electricity consumers: the winery refrigeration systems, the air compressors, and the building heat pumps.  In addition, indoor temperatures were recorded for the larger rooms in the winery building, as well as the local outdoor temperature.  The glycol temperatures were recorded to indicate whether the refrigeration system was performing adequately during the hot days of summer, when cooling the juice from crush places the most demand on refrigeration.

The audit data showed the refrigeration system was limited on hot days and unable to maintain ideal control of the glycol coolant temperature. During the hottest days of the audit period, particularly during crush periods when grape juice was being chilled, the glycol temperatures rose above 50 F.  During the night, the glycol temperature was eventually reduced sufficiently so that the wine and juice temperatures were maintained within an allowable range. 

The first impression might be that the refrigeration system needs more capacity.   However, since the wine tanks are not insulated, the refrigeration system is “running in place” on hot days just making up for the heat gains from the surroundings. If the bulk wine tanks had been insulated, the refrigeration system would likely have been able maintain the glycol system at the correct temperature.

In the twenty years since the Kunde building was designed, major improvements have been made in both the California building energy code minimum compliance and best practice design.  Professional associations for architects such as the US Green Building Council and the 2030 Challenge are now promoting building designs that will use a fraction of the climate control energy needed for 1990s era buildings.  A key part of this revolution in building design is the computer modeling that allows an architect to predict the energy use of a building, and test different energy efficiency improvement strategies.  George Beeler used a computer model called eQUEST to simulate the energy use of the Kunde building in its present form.  The model’s predicted energy use was compared to the energy use measured during the audit, to verify the computer model was working correctly. The computer model was adjusted accordingly.  George then predicted the effect of building improvements such as  night and economizer cooling, daylight harvesting controls (which make daylight use more efficient and pleasant), more efficient lighting and occuopancy controls, solar space heating, better windows and skylights, sealing air leaks, improving insulation and more efficient heat pumps,.  All these improvements were estimated to reduce building lighting, cooling, ventilation and heating energy use by 80+%.

The analyses of the winery refrigeration system and the building show that dramatic reductions in utility power purchases (and the associated greenhouse gas emissions) were possible with efficiency improvements.  The next question is – at what cost, and what is the return on investment? 

Since the refrigeration system is the major energy consumer, a financial analysis was made on four options for improving its efficiency.  As noted before, there is an operational need to maintain better temperature control during hot periods, particularly during crush.  One option would be to replace the existing refrigeration system with one that is more energy efficient, with enough capacity to meet the existing demand.  A second option would be to insulate the wine tanks, which would reduce peak demand enough to allow continued use of the existing refrigeration system.  Finally, an integrated design approach combines insulation and more efficient refrigeration that is significantly smaller, and achieves the 90% energy savings predicted in the engineering analysis. Of course, energy efficiency improvements to both the building and the winery process will require a significant investment.  The following table summarizes the financial implications of these scenarios:

This analysis indicates that the financial incentive for tank insulation is very attractive – a simple payback of less than two years.  However, financial incentives alone are not as attractive for the Integrated scenario, which yields the greatest energy savings.  However, if Kunde’s goal is to eliminate their GHG emissions from utility power, how do the costs and benefits of efficiency improvements compare to purchasing a solar PV system to power the entire facility?

Even before considering solar PV’s cost, how large would the solar array have to be to power the existing winery and building?   This aerial photograph of the Kunde property, with two sizes of PV solar arrays shown as the overlaid green squares.  

Generating the power needed by the winery and building – with no improvements in efficiency – would require over 5 acres of PV solar arrays. If producing vineyards had to be removed as shown in the picture, this would significantly impact revenue.  However, with all the efficiency improvements the DesignSmart Group believes are possible, a much smaller solar PV array (less than half an acre) could be used, which could be placed over the existing visiting wine taster’s parking lot for shade. (The integrated design approach always looks for multiple benefits.)

If the goal of a winery is to eliminate GHG emissions from utility power (also known as a “zero carbon” scenario) then what makes the most financial sense?  For Kunde, the cost and savings of on-site solar PV would be combined with efficiency measures.  However, it is not trivial to translate the financial benefits to a single number.  Solar PV has significant tax incentives, in the form of a tax credit, and an accelerated depreciation allowance.  A net present value analysis with a 20 year time horizon was chosen to compare five “zero carbon” scenarios: 1) Baseline – add needed refrigeration only; 2) Solar PV supplies power for baseline winery; 3) New refrigeration equipment with solar PV; 4) Tank insulation with solar PV; and 5) Building, refrigeration, and tank insulation combined, powered with solar PV.

With all the scenarios shown, if  Kunde’s goal is 100% zero carbon (renewable) power, in all proposed cases they save money over the baseline in combined capital and utility costs. The tank insulation plus solar PV scenario has the greatest net savings, since tank insulation has such a low capital cost. 

Beyond the basic dollars and cents, there are other significant benefits to the Integrated scenario, which combines all the efficiency measures with solar PV.  The existing refrigeration system will eventually need replacement, and will likely require more maintenance (and be less reliable) until it is replaced.  Replacing it now will save the extra maintenance costs, and give more reliability to its operation.  The building improvements will improve employee comfort, fix the sunny day overheating of the wine tasting and conference room area, and can have a positive effect on employee productivity.  The building improvements could also be part of a green marketing strategy.  Displays of the building’s energy saving features can be added for visitors who are interested in whether or not wineries are walking the “green” talk.

In conclusion, the determination of the costs and benefits of a zero carbon energy strategy are not simple.  At Kunde, the DesignSmart study has shown that efficiency improvements combined with renewable energy will yield the greatest long term savings to the winery owner. The economic balance between efficiency improvements and renewable energy will differ with each winery.  However, the capital costs of achieving zero carbon energy through renewable energy and efficiency improvements can be in the millions of dollars.  Winery owners should undertake a careful study of their facility before embarking on a course of action.