Adsorption Cold Storage for Mobile Applications
Round 1
Reviewer 1 Report
The topic is interesting and can be useful for increasing efficiency of power consumption in mobile application. Reviewer has only two concerns about the visual form of the paper.
- Nomenclature should be on top of the paper and should explain all the symbols used in the equations. It needs to be changed.
- Almost all presented graphs are distorted. It is especially visible on text. Additionally, on the graphs with two vertical axes, there is no clear indication, what line belongs to what axis.
Reviewer thinks, that after these two correction, paper can be published.
Author Response
The nomenclature has been moved on the top of the paper and modified. All the figures have been updated. Clear indications, to better understand what line belongs to what axis, have been added.
Reviewer 2 Report
This paper aims to present a concept of adsorption cold storage based on two innovative adsorbents for different reactors. It is generally written and detailed work in terms of the experimental work. Here are some minor suggestions.
1. Please try to merge some paragraphs in the introduction.
2. Please revise the format of table 3 which is different from the others.
3. The main research work is based on a previous experimental rig. The results are good and reasonable. But I cannot see the big relationship with mobile applications. In the charging process, the heating source should be variable, which will have an influence on the sorption capacity. Also, in the discharging process, it is welcome to give an analysis of cold cabin inside, i.e. the internal temperature changes. Besides, it is better to show the technical and economic influence of this additional adsorption system when compared with original one.
Author Response
- Some paragraph in the introduction have been merged
- Table 3 has been revised
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The presented prototype has been specifically designed for mobile applications. The volume, the adsorption material mass and all the installed devices have been considered taking into account the constraints related to the use of such a component in a small vehicle, as shown in figure 1. The heating source is variable only during the ICE warm-up cycle, which is a very limited part of a normal duty cycle (from 10 to 20 minutes depending on if we consider gasoline or diesel engine). After the warm-up, the engine normally works at a temperature, almost constant, between 85°C and 90°C. In our tests, we have considered two different driving temperatures, but we have intentionally neglected the warm-up cycle because the engine efficiency, in this period, is lower and normally the manufacturers try to reach the operative temperature as fast as possible. We try to better explain this concept modifying the Concept description as follow:
The main idea behind the study conducted and here introduced, is the possibility of using waste heat from the I.C.E. of a small vehicle for the transport of perishable goods (e.g. food or medicine) to refrigerate the load compartment during the parking phases for a limited time (1-2 h). While the vehicle is running, the heat taken from the engine-cooling loop is used to “recharge” the cold storage system located near the refrigerated compartment. During the stop, when the internal combustion engine is no longer able to supply mechanical or thermal energy, the system is “discharged” to generate the cold necessary to maintain the temperature in the load compartment (Figure 1). The “recharge” phase considered in this study hypothesizes that the ICE is at the normal working temperature (85-90°C) which is maintained almost constant by the engine cooling system already installed in the vehicle. The ICE warm-up cycle was not considered due to the lower engine efficiency.
We have considered different cabin inside temperature during the discharge phases, variable from 10°C to 20°C when the driving temperature is 90°C and from 10°C to 15°C when the driving temperature is 85°C. Unfortunately, we have not the possibility to test the prototype using a cabin; therefore, we were not able to acquire the cabin inside temperature, but only to assume it at some constant levels. Anyway, we will try to better explain this concept modifying the text as follow:
In Figure 8 (a) and (b), the effect of evaporation temperature and driving temperature are shown for discharge power and recovered cold energy, respectively. All the tests are performed for a charge and discharge duration of 900 s with a condensation/adsorption temperature of 30°C. This part of the experimental test was carried out with the aim to evaluate the effect of two possible ICE operative temperatures (85°C and 90°C) as well as the effect of the cabin inside temperature, assuming it at different constant levels (from 10°C to 20°C). It is visible that higher driving temperature are beneficial especially to discharge power, since an increment of about 15% can be obtained. The average discharge power measured, especially with 90°C driving temperature, is as high as 850W. By moving from an evaporation temperature of 10°C to 15°C, a great increase is observed, while after such temperature, a plateau is reached. For the lower driving temperatures, discharge power in the range 500 W to 730 W has been measured. The effect on recovered energy, though smaller, is still recognizable: for 85°C tests, energy recovered lied in the range of 170 to 220 Wh, while for the higher temperature, the maximum energy recovered was about 220 Wh.
From the technical point of view, the proposed solution is fully integrable in a common small commercial vehicle, because it was designed considering the physical and technological constraints of this kind of application. From the economic point of view, we estimate that a cut of 15% of the operational costs is feasible, especially after the massive diffusion of similar systems. A favorable cash-back could be reached, comparing the proposed solution with the actual systems, but a cost estimation, at this development time (TRL between 4 and 5) could introduce too much uncertainty.
