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Column for Ch & K – Energy-efficient refrigeration or – NOTHING?

There are nuclear power plants in France, transmission is limited in Scandinavia, there is little wind in the Atlantic, Germany is short of gas, and Poland is short of coal. Energy market analysts have been predicting the current situation for at least several years. We are talking about electricity shortages and the resulting astronomical prices per MWh.

So what is more important – cheaper energy or lower energy consumption?

Contrary to appearances, the lack of energy is not alien to our industry. I first encountered him in 2010, when I participated in the construction of a hypermarket in the outskirts of the city far to the east – beyond the Urals. The client was faced with the choice of building the most efficient cooling installation with full heat recovery or resigning from the investment as a whole. I have had such limitations regularly since then, and I believe my readers will too. However, it was only a local phenomenon, not significantly affecting the energy price.

In my opinion, your biggest advantage by standing up for the tender – an ace up your sleeve, is not meeting the requirements of EU regulations or ecology (otherwise right), but reducing the demand for electricity and enabling the client to carry out his investment. As I wrote above, we already have experience in this.

Meanwhile, astronomical energy prices. They should be treated as an additional leverage for our offer, giving faster payback for flooded system, heat recovery, hot glycol defrost, etc.

According to my calculations, most energy improvements today have a payback time of well below four and sometimes even around two years. There is no point in looking for such fast payoffs elsewhere!

How much does it cost to cool a plastic brush? – article for Plast Echo

Another article on energy-efficient cooling was published in the February issue of our favorite magazine for the plastics processing industry – PLASTECHO. Full text and audio version below.

Winking at my lecturers from Kozminski University, I answer: “It depends.”
It depends on what cooling it requires, how much the finished product weighs, in what temperature range we move, how the cold is produced, what is the loss of its transmission … and only finally how much the reader pays for a kilowatt-hour of electricity. I mention the electricity rate as the last criterion because for different cooling systems the difference in electricity consumption is up to 50% – which is more than the increase at the time of writing this article. As it is easy to see, there are many variables. And while it is easy to determine the investment costs of buying a chiller or building a central cooling system, the cost of operating this system, and consequently the cost of cooling the title “brush”, is very difficult to determine. It is often part of a total electricity bill and mixes with the energy used to power machinery, lighting, and more. Of course, the example given is not a rule, but shows a general tendency.

This text is an extension of another article by me, which appeared in one of the previous issues of “Plast Echo”. So let’s return to the analysis of a 500 kW chiller. Let us assume that two devices operate under the same conditions, with full load, all year round. We produce water at a temperature of 10/15 ° C and as a base we consider a device based on a popular synthetic factor (r410a), and compared to r744 (CO2). Both systems cool the water, the circulation of which is provided by an 8 kW pump. Please note that we have lowered the water temperature in relation to the previous article. Both chillers will produce 4,380,000 kWh of cooling for one year. The F-gas machine will consume 853 185 kWh of electricity during this time, and 474,063 kWh of electricity for CO2. This energy will be used by compressors, condenser fans (or gas cooler), pumps and, in a marginal amount, for automation and control. By making simple calculations, the cost of 1 kWh of cooling for the systems under consideration is as follows (1 kWh of electricity = PLN 1): r410a – PLN 0.18 / kWh of cooling, r744 – PLN 0.10 / kWh of cooling – 44% or 379 savings PLN 122 per year.

HOW MUCH FREE-COOLING SAVES?

Free-Cooling – i.e. free cooling – consists in cooling the process water with the use of outside air when the ambient temperature is sufficiently low. In the case of water 10/15 ° C, we will usually have full cooling power for an outside temperature of about + 2 ° C. Although, unfortunately, I often see dry coolers with a delta of 12 or more degrees Celsius. Due to the risk of water freezing, Free-Cooling often works with glycol with an additional exchanger, which reduces its efficiency. In such a system, the operating time of the compressors will decrease due to the extended operation of the fans, additional pumps and losses on the exchanger. The F-gas system will consume 753 226 kWh of electricity, and the CO2 one will consume 444 458 kWh. The complete data is presented in Table 1.

As we can see, depending on the method of production of cold, it can cost us from PLN 0.09 to over PLN 0.18 for each kWh, and even more in the case of used cooling installations. Maintenance is not included in this value. Since we have established the unit cost of cold, let’s ask how much is needed to cool the title “brush”? In the process of plastics processing, the produced detail, oil and mold are cooled. There is also a loss of coldness in its transmission. In simpler words, it means undesirable heating of cooling water in pipes, pumps and tanks. For the purposes of this article, I made theoretical calculations and consulted the manufacturers of injection molding machines. I should emphasize that the required cooling capacity will vary significantly depending on the material, production temperatures and many factors that the reader probably knows very well. Therefore, further data should be treated more as a description of a specific case than universal knowledge. As a good practice it is assumed that in the production using cooled molds, the chiller should have 50% of the electric power of the injection molding machine, and it is from this value that I used for further calculations. Producing 4 brushes weighing 90 grams per minute, 21.6 kilograms of material will be processed in an hour. Such a machine requires a 20 kW chiller. This gives 0.926 kWh cooling / kg or 0.083 kWh cooling per brush. The final cost of cooling in various configurations is presented in Table 2.

To sum up: the annual average cooling of the title brush costs between 0.8 and 1.5 groszy for each piece of the finished product. In summer, it will be closer to 2 to 4 groszy, while in winter, the cost will be less than the above-mentioned values. Taking into account the unit cost, the aforementioned value is not large, but it is worth paying attention to the graph showing the operation of the mentioned devices on a 15-year scale – and this is (at least) that the chiller should work for.

So we are talking about the potential savings (or unnecessarily spent money) at the level of over PLN 6.1 million, assuming that the price of energy will not increase. This value is many times greater than the additional cost of better refrigeration technologies.

UNDEDUCED COOL POTENTIAL – HEAT

Thermodynamically, cooling is about removing heat. Through the chiller cooling circuit, this heat is finally removed to the environment, i.e. it is treated as waste. And as I will show below – it is a very valuable waste. The considered 500 kW chiller will emit at least 600 kW of heat to the environment (at maximum load conditions), which amounts to 5.25 million kWh per year. This heat obtained from gas at the rate of PLN 0.25 / kWh will be worth PLN 1,314,000 every year. From the “hot side” point of view, it will be a heat pump that can meet the needs of up to 120 homes. A significant difference between the aforementioned chillers is also hidden in ecological issues. However, this is a very broad topic and I will leave it for the next article.

In summary, each chiller is both a cost and a potential. The cost on the cooling side, which consists of the investment and operating costs, and requires far-reaching optimization. Only the sum of the costs actually reflects the funds allocated to the chiller and the potential profit on the heating side. Which system to use depends on the individual needs of each client. I believe that in the plastics processing industry, the time of super-efficient chillers is fast approaching. Or maybe it has already come?

 

 

Maurycy Szwajkajzer

for Plast Echo February 2022

Cooperation with professionalnezakupy.pl – how to buy refrigeration?

As consultants in the field of refrigeration, we often support customers in purchasing processes, which is why we have started cooperation with a friendly blog www.profesjonalnezakupy.pl.

The first column on the topic of buying refrigeration can already be read or listened to below.

A word of introduction

According to a survey I conducted at the end of 2019, the priorities of bidders (refrigeration companies) are set in the following order: low purchase price (40%), reliability (32%), low energy consumption (19%), adaptation to needs (7% ), simple design (2%). Ecology got no vote. Therefore, by sending a low-detailed inquiry, offers from suppliers will almost certainly follow this key. The installation will be as cheap and failure-free as possible. In the event that we care about something more, e.g. a precise match to a given need or ecology, we will need to specify the query accordingly.

Stages of the procedure

All the rules given below apply to the purchase of a refrigeration system directly, as well as to the general contractor of the entire facility. The cooling installation is carried out similarly to most construction works, the good old school of preparing and implementing such investments gives easy answers. Implementation can be divided into a few basic stages:

  • Preparation of the inquiry along with sending it to bidders
  • The tender process ended with an order and signing of the contract
  • Preparation of works
  • Implementation of works, including staging
  • Collections Warranty and servicing

In this column, we will focus on the first two points on the list above.

In the case of bidding, the situation is simple. As we prepare the inquiry, this is the answer we will receive. With an imprecise inquiry, we will receive incomparable offers with a very large range of prices. The first step is to identify the client’s needs. They result from direct consultation, the architecture of the facility and the type of business. On their basis, I prepare a tabular offer form in which the key features of the refrigeration system are specified, including:

  • Type of technology
  • Cooling power
  • Performance standards
  • Preferred component manufacturers
  • E.t.c.

The table for works worth EUR 1 million will contain around 50 well-thought-out items. An annex to the offer form should be an architectural (room) plan, a model contract and a preliminary schedule. The bidder completes and submits an offer on our form. Thanks to this, the customer receives homogeneous offers that can be easily compared. Tender processes that I prepared according to this method had a price spread usually below 15%. Compared to 200% with a simple inquiry without an offer form.

A well-prepared inquiry and offer are an incredibly powerful tool in the hands of a buyer.

Effects consultant role

In my opinion as a juxtaposition consultant it is determined that the bids submitted are appropriate and meet the technical requirements. Yes, offer handover to the client, usually without taking into account the final price setting. The documents we have created also define industry boundaries, which allows you to use non-program fees where they meet.

Undoubtedly, the places that are most often viewed with the standard source are:

  • Electrical installation of the refrigeration system
  • Substructures
  • Refrigerant detection device or man-in-chamber alarms

In addition to being characteristic, it is also cheaper to insure.

Refrigeration is not just technology. This industry is surrounded by many general construction regulations, the Office of Technical Inspection, environmental protection and others. It is also my responsibility to ensure that all formal requirements are met. This is particularly important in terms of security, insurance costs and resale value.

Summary

To sum up, the cost of the consultant’s work is between 1-3% of the value of the work carried out and it is an investment that pays off already at the time of the first price negotiations. Therefore, a well-prepared tender (I encourage you to check the article – How to Organize a Tender?) is a stable basis for successful and peaceful implementation, without all-night meetings and delayed acceptance.