ZEMCH 2019 International Conference Proceedings April.2020 | Page 286
1. Introduction
1.1 Houses use more energy than commercial buildings
The vertical axes of Figure 1 show the Energy
Consumption in the US from year 2000. The values
in the top figure, by the commercial sector, is half of
that in the bottom figure, which shows that
consumed by the residential sector.
The plots with the largest amplitude are for
natural gas, which is the main energy used for
heating, indicated by the peaks in the winter
months. The plots with the second largest
amplitude are for electricity, which. has small peaks
also during the winter months and a larger peak
during the other half of the year, i.e., during the
summer months, which can be indicative of energy
used for cooling.
1.1.2 Limitations in the use of hydronic radiators
(HR) for home cooling
Figure 1. Energy Consumption in the US.
Water cooled by radiation to the night‐sky to 23°C was used for the HR at the experimental
building in Kuching, Malaysia, Measurements conducted in mid‐2017 showed that indoor relative
humidity reached 80% and there was condensation on the surface of the HR. Moreover, occupants tend
to sweat, and this latent metabolic heat cannot be transferred by radiation to the HR. Therefore, besides
this HR, devices to ventilate and possibly dehumidify would be needed, making the HR inappropriate
for small dwelling building in hot climates,
1.1.3 Hydronic systems vs air systems.
The indoors can be heated or cooled by air or water. Air systems is more conventionally used, but
to move water requires less energy than to move air. While the specific heat of air is around 993 Jkg‐
1K‐1 that for water is 4200 Jkg‐1K‐1, which is 4.23 times more; and while the density of air, depending
on temperature and humidity, is around 1.275kg/m3, that for water is 1000kg/m3 or 784 times more.
The volumetric heat capacity for water is thus about 3320 times that of air. When centralized systems
are used, the circulation of air requires large ducts and big fans, but to circulate water only small pipes
and pumps are needed. Therefore, this project choses renewable sources to heat water for low
temperature hydronic radiator (HR) and radiator‐convector.
1.2 Literature Review
Qian Wang et al [1] ishowed that low temperature hydronic can improve the thermal performance
of five retrofits to an acceptable level. Dietrich Schmidt et al [2] pointed out that currently 12 research
institutions from 8 countries are participating in the research to use low temperatures in district heating.
Mats Dahlblom et al [3] evaluated a feedback control method for hydronic heating systems based on
indoor temperature measurements. Matjaž Prek and Gorazd Krese [4] presented an experimental
validation of an improved heat output regulation concept for multi‐panel radiators and showed that
the implementation of the modified water flow arrangement significantly improves the transient
response of heating radiators in terms of reduced time.
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ZEMCH 2019 International Conference l Seoul, Korea