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System Design: Solar Thermal Power Generation
I've hit a wall in my engineering ability (as a structures guy) when it comes to thermal dynamics.
In short, I want to replace a custom heat pump's compressor with a proprietary expander tied to a generator, and use Solar Thermal as the heat source to drive the temperature delta thereby generating electricity.
I'm challenged with sizing the component of the whole system in order to build a demonstrator - additionally, I know there are little things in the system design that are needed, but don't know what they are. I am hoping I can get some help.
So here is the concept:
Evacuated Solar Thermal Tubes running dowtherm 10 (or eq.) on a drain back loop into a series of tanks with heating oil. Heating Oil tanks are intended to store enough heat to keep the working fluid @ or above temp for 6-8 hrs. Then there is a loop between the oil tanks and a plate heat exchanger - the loop should stay above 200c for as long as possible. the goal is to generate power at the peak periods of 7-9pm and 6-9am.
Working fluid passes on the other side of the plate heat exchanger and picks up heat (200c+) then pass over the expander - the pressure/phase change driving the expander+generator. The working fluid then passes through a "cooling" plate heat exchanger. To get the bare minimal energy generation, there should be a temperature delta of 30c between the hot and cold sides of the expander. I don't know the pressure drop over the expander - id like help finding out what it needs to be - in order to adjust the mechanical design of the expander. I don't know what the mass flow rate needs to be.
The cooling plate exchanger side has a target of heating water for domestic use - assuming the water should maintain between 100-140F temperature - and assuming a 40ga change over 2x a day (i.e. 2-3 showers a day)
I need to know how many SF of Solar Thermal Tubes I need to achieve the goal of 5Kwh output. I do know that this type of system typically is between 10-12% efficient on energy conversion. If we could get it to 18% efficient - it could be a seed change.
I'd like to be able to figure out: pump sizes, flow rates, thermal storage amounts for the oil tanks, and how much water i need keep in storage (100ga?) and....
Well - by now you can tell I am pretty much out of my depth when it comes to this sort of thing. Help would be appreciated - and ....equations are always appreciated. I just don't know how to calculate between the heat transfers and flow rates....Anyway.
Here is to a new year with better energy possibilities!
- Tryden
Tryden
Trane Air Handler Fan Constantly Running
I have an old Trane air handler ('92) whose blower immediately and constantly turns on as soon as power is turned on to the air handler. The fan will run despite turning off the thermostat or unplugging G from the board.
I think it is the relay that is faulty and the NO connections remain stuck close, causing the fan to constantly run.
I found a similar looking DPDT switch on Amazon, but it doesn't seem to include any time delay features and not sure if it would be compatible.
I tried finding a replacement online however it seems that the relay is discontinued. There are some posts online that state an appropriate replacement would be the RLY02807 time delay relay, however I'm not entirely sure. Here is its installation manual.
Honeywell ST82U 1004
R8222U 1071
21C144385P01
12AFL 72ALR 120 VAC
6AFL 36ALR 277 VAC
3AFL 18ALR 480 VAC
15AMP RES 277 VAC
10AMP RES 480 VAC
Re: Prevent mold in mini-split heads
Not the easiest thing to take a picture of but the blower wheel looks like what you would expect for something that sits in pretty much 100% RH most of the time. That is all dust on the surfaces. About 6 years ago the bearing went on the blower and did clean it once when that was replaced.
Not a fan of wallmount design, they really should have put the blower before the coil like most other units out there.
@jpm659er The blower not shutting off is by design. There is no way to measure room temperature otherwise and most people won't spend the extra money for a remote.
This is not really an issue if the unit is sized somewhat correctly and connected to an outdoor unit with good turndown (that is not a multisplit). From the power use on those units, they are cooling pretty much all the time, this means the supply air is bellow 50F all the time.
Kaos
Re: Trying To Estimate Heat Pump kWh Usage
The last time I filled my tank I paid $4.11 per gallon. That equates to $0.35 per kWh, which sounds about what you'd pay in Mass.
Why is my radiator cold? this weeks video
In this weeks video, I discuss many reasons why the steam radiator is cold. Im sure you can add one or two other reasons.
Re: Well pump issues
Has anyone checked the well itself? Over time, it is possible for the well screen to become clogged. This will result in the water level in the well dropping further than it did when it was new, and the pump performance will be affected since it has to lift the water farther. Another possibility is that the overall static ground water level has decreased over the years, with the same result.
Since this is a deep well jet pump, it might be worth looking at the water level in the well with the pump off (the static level) and the water level in the well with the pump on (called the dynamic drawdown). Since you do not see bubbles — and the pump shuts off at 40, though it takes longer than it used to — you are not likely drawing the water down far enough to dewater the well — so that's good. But even so, you may need a pump capable of a greater lift and shutoff pressure.
Re: Trying To Estimate Heat Pump kWh Usage
We're mostly considering the heat pump because she'd like to get AC other than her existing window units.
JustinS
Re: Trying To Estimate Heat Pump kWh Usage
Your math looks right.
This post explains how to do a more detailed modeling:
Re: New tank, single top line, do i need a shutoff?
The tank should sit on a concrete pad , The moisture from the bare ground will rot out the bottom of the tank. Leaves that collect under the tank will do the same. You want to protect the outside from rusting . Rustoleum any scratches that end up in the paint .
Use the bottom tap rather then the top .. Top feed tanks will collect water below the dip tube . The layer between oil and water an algae will grow . The algae feeds off the oil and poops out "Sluge" . The kicker is the algae can't digest the sulfur in the oil and the sludge is a sulfuric acid in base . Probably the reason for the new tank…..The Roth tank has a plastic liner to protect the steel . The Roth will build up sludge too . You have to keep a Roth tank treated to prevent oil flow problems..
Pitch the tank 1/4" down to the valve to drain off any collected water in the tank . Go to HomeDepot and have them cut and thread two sets of 1.25" nipples for the legs with a 1" difference to achieve the 1/4" pitch . And while you are on that isle pick up 4 x1.25" flanges for the legs foot… You say your tank sits 2' lower than the burner ? Now is time to bring up the oil level …
Replace the oil line…. Run a new contained oil line . Copper tubing with a plastic cover. This is a must have for the crawl space oil line run. Trust me on this one , every oil guy here would have stories ..
A fireomatic is required for parts with gaskets like filters, pumps and tiger loops …
As stated above , run the oil line with downward pitch into the house. Any water with the pitch of the tank and the oil line will end up down stream inside the house past the freeze zone ..Inside add the fireomatic valve and service filter ..
New tank new oil…
Hope this helps
Big Ed_4