[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [EnergyPlus_Support] Can Radiant system save energy?



I think one of the main advantages of using radiant systems is that you separate the conditioning of the space with the conditioning of the ambient air. With radiant systems you can deliver the air into the room at ambient temperature and use the ceilings to heat up the rest of the room. This will help avoid all the reheat energy that comes from using a VAV. I believe an NREL study showed that by separating the ventilation from the zone conditioning it was possible to save up to 30% of the energy in the building. I do not have the study to hand so I apologise if this isn't the case.

I have found that in Europe radiant systems are very common this is because in general the building envelope is better, reducing the heating load. 

The second advantage particularly with heated ceilings/ floor is the thermal comfort of the occupants. 

None if this helps you size your systems but I thought it might add to the discussion.

Annie

Sent from my iPhone

On Jul 21, 2014, at 6:54 PM, "RobertWichert robert@xxxxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

 

Interesting question.  To me anyway.  I have a project in San Francisco where the loads using ASHRAE Handbook methods are well above the radiant capacities in the apartments, but there has not been a huge outcry of being cold all the time.  Granted, San Francisco is pretty mild (very mild), but the loads being twice or three times the capacity, well, I have to guess that it's because the loads using ASHRAE methods are met by lower radiant heating capacity than air system capacity.  This seems pretty intuitive, really, but I have not found any standard guidance yet (still looking).

So at the risk of being shown to be wholly ignorant, can anyone point me towards any design documentation regarding radiant heating capacity and how to meet heating loads calculated using "air system" methods?  ASHRAE guidance, perhaps?



Robert Wichert








On 7/21/2014 12:26 PM, HJ wanghaojie630@xxxxxxxxx [EnergyPlus_Support] wrote:
 

I use E+ to calculate radiant system compared to traditional VAV system.
The results showed that radiant system uses more heating energy but less
cooling and energy. (of course less fan energy and more pump energy). In
total I could see some energy saving but I would assume this will
diminish in a heating dominate climate. I wonder what is the energy
benefits of a radiant system? I could understand the heating energy
increases because we have more envelope loss. But why then the cooling
energy decrease? This looks like a little inconsistant to me.

HJ




__._,_.___
Posted by: annie <anniemarston@xxxxxxxxxxx>


Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx

The primary EnergyPlus web site is found at:
http://www.energyplus.gov

The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/

Attachments are currently allowed but be mindful that not everyone has a high speed connection.  Limit attachments to small files.

EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.




__,_._,___