Hi Everyone,
A project I'm working on has Solar Collectors as a primary source of service water heating with electric heaters for backup. I had modeled the service water heating electric system as identical in IES-VE and had input the energy contribution of the Solar Collectors in the Renewable Energy section of the MEPC. We are also targeting the Renewable Energy credit based on the Solar Collectors contribution.
A Design Preliminary Review Comment we have received reads:
"The narrative provided in EAc Renewable Energy Production credit form indicates that the solar collectors are installed on the roof of the project. However, the floor plans and renderings provided in PI do not show any indication of these solar collectors being installed.
Provide documentation, such as drawings, to show the on-site renewable energy systems details."
The question I have is whether this means the approach I've taken to model the service water heating is accurate and we'll not receive any further comments on the modelling approach if drawings showing solar collectors are submitted along with a narrative response? Or they will reanalyse the modelling approach based on the solar collectors drawings submitted?
Any input or thoughts are appreciated!
Junaid Mujahid
Junior HVAC Design Engineer - SustainabilityPNC Architects
2 thumbs up
January 29, 2025 - 6:56 am
identical in both the baseline and proposed models*
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5925 thumbs up
January 29, 2025 - 9:48 am
The comment is simply seeking verification that the solar system was installed. Sounds like they are not questioning your savings calculation. So the answer to your first question is yes (assuming this was the only comment you received on this system), the answer to your second question is no (unless you provide them with additional information that contradicts or calls your original calculation into question).
Junaid Mujahid
Junior HVAC Design Engineer - SustainabilityPNC Architects
2 thumbs up
January 30, 2025 - 5:25 am
Appreciate your response!
Is it possible to use an external software solar simulation report from the supplier of the DHW heating system as a replacement for modelling it in the Energy Modelling software?
To clarify, I have modelled the baseline DHW heating system in the Energy Model. But instead of modelling the proposed system also in the energy model, I'd like to use the external solar simulation report which indicates the solar energy contribution to DHW and the energy consumption of the backup electric heaters.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5925 thumbs up
January 31, 2025 - 1:49 pm
For something like service hot water you can easily calculate the energy use/savings outside the modeling software and apply it to the results. That works because the service hot water system does not create any effect on the thermal loads of the building. Any system that effects the thermal loads must account for them and is typically required to be modeled within the energy modeling software. Make sure you provide a detailed narrative and the calculations that were used to show the savings.
Junaid Mujahid
Junior HVAC Design Engineer - SustainabilityPNC Architects
2 thumbs up
February 3, 2025 - 12:40 am
We have received a solar simulation report that indicates the energy use of the proposed hot water system. But obviously they do not compare it with a 90.1 baseline system. The only objection reviewers can have is that both systems (proposed & baseline) should be modelled on the same software to ensure reliability of reported savings. Is this something to worry about because we have modelled the baseline system on IES-VE with the baseline energy model?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5925 thumbs up
February 3, 2025 - 4:39 pm
You should treat this as an exceptional calculation. Calculate the baseline and proposed usage in IES-VE without the solar. Calculate the solar savings in the way that you have. Then provide a narrative to explain the calculations and justify the claimed savings. In my experience it is typifcal that a solar hot water system would produce about an 75%-80% savings if sized in a cost-effective manner.
Junaid Mujahid
Junior HVAC Design Engineer - SustainabilityPNC Architects
2 thumbs up
February 5, 2025 - 2:27 am
I deeply appreciate your valuable insights Marcus! Just one more doubt on this:
What about the heating capacity of the proposed system? Currently it is undersized considering majority of the hot water demand will be satisfied by the solar collectors. So if the actual undersized capacity of the electric heaters is modelled, it will not be able to satisfy the demand without solar contribution. Would it be more reasonable to auto-size both the proposed & baseline systems capacities and demonstrate savings over that using the external solar simulation report?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5925 thumbs up
February 5, 2025 - 9:06 am
When you engage an exceptional calculation you often model the baseline and proposed systems identically in the model. In this case model the proposed identical to the baseline so auto-sizing both would be fine.
Junaid Mujahid
Junior HVAC Design Engineer - SustainabilityPNC Architects
2 thumbs up
February 6, 2025 - 9:25 am
Will follow this approach, thanks once again!
Junaid Mujahid
Junior HVAC Design Engineer - SustainabilityPNC Architects
2 thumbs up
February 20, 2025 - 6:10 am
Hi Marcus,
I have followed the above modelling approach and am now finalizing documentation. I wanted to know if there is any specific guidance (in LEED or 90.1) on how "exceptional calculation" methods like these should be reported in the MEPC and/or the simulation report. Or should this not be mentioned at all since it is a standard approach for modelling Solar Collectors for DHW?
Appreciate your valuable insights!
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5925 thumbs up
February 20, 2025 - 12:52 pm
In the Performance Output tab you will find a section for reporting exceptional calculations. Make sure to also include a thorough narrative explaining the baseline assumptions, the proiposed system design, and how the savings were calculated.
Junaid Mujahid
Junior HVAC Design Engineer - SustainabilityPNC Architects
2 thumbs up
February 21, 2025 - 12:01 am
But using that is counting the savings as double since they are reported in the On-Site Renewable section as well as we are attempting that credit too. Anyways, I'll give the narrative explaining the modelling approach. I hope the reporting method will be understood as long as the system and calculation method is explained properly.