Diesel engine as generator question?
- Thread starter BAD ORCA
- Start date
That is a really great answer that actually gets to the question. Of course, the follow-up (for me) is: Then why don't diesel engines decrease air intake proportionately?
I don't think the point was lost. I think, though, that the assertion that it is somehow cheaper than solar is probably somewhat dated (and probably has not been true for some time). I power my entire home with about $12k worth of solar (including professional installation) and charge an electric car (so no gasoline used by that car), and still produce a bit more than I consume in a year. It should last 30-50 years, and it guaranteed for 20. (It might actually be 30 - I don't recall.) I think that puts the up-front cost about the same as a comparable diesel generator with only a 5-year warranty, but without the additional costs of maintenance and fuel.
There is no way diesel can compete with that, economically. In fact, we are no longer charging that car, so now we even produce a surplus on all but the darkest days of winter.
The point is taken that diesel is efficient, as fossil fuels go, and it has some distinct advantages. The sticking point is the assertion that it is cheaper than solar.
The point is non-sensical. Yes, if you are running your engine for propulsion, then sticking on an alternator is inexpensive (but not free) power. It is why all engines come with an alternator. His point is to stick on a very large expensive alternator (Integrel starts at $12K, and doesn't include the massive 48V LFP bank required) and use some software to keep its output within the optimal load band for the engine. This is cute, and can help a small engine, but the extra 7hp to operate a 4800W alternator is not a burden for most engines 30hp and above, and the "optimization" potential rarely comes into play. Make no mistake, though - Integrel is designed primarily as a genset when not under propulsion. Also keep in mind that Calder has financial interest in Integral.
But given all of that, he still cannot make the point that it is cheaper than solar. Solar still works when under propulsion. It works all the time for free after the initial purchase. More to the obvious point - it works when the engine isn't running, when an alternator cannot.
There is no situation where an alternator is cheaper than solar.
He can make the point that a HO alternator is cheaper than a genset, and I would agree because we got rid of our genset for a HO alternator and are now getting 2x the charging output at 1/2 the diesel burn.
Mark
No, no, no, no. For your application (and all other applications that come to mind), size the engine appropriately for the boat. Don't worry about load. Put a large alternator on it and run it for power generation at low speed whenever you need. When you are underway, run it at high load (rpm) for 30min or so, and it will stay healthy. Really, this whole engines will be ruined charging at anchor with an alternator is way overstated.
Particularly for you. What size engine can even fit in a Mariner 36? 30-40hp max? You won't be glazing cylinders or coking up elbows using 4-6hp to run a HO alternator on it for an hour a day at anchor between uses for propulsion.
Before cheap and ubiquitous solar, almost everyone ran their engines at low speed for hours to operate a tiny alternator for charging, and very, very few people experienced any issues doing this. The stories of ruined engines and regular rebuilds just never existed. And this was the worst case scenario. Nowadays, you can operate an alternator on the same engine that outputs 10x the charge - or provides the same amount of charge in 10x less time. So the TIME the engine is running at this "damaging" low load is a very short time. You probably will operate your engine under light loads for longer periods of time just idling and moving slowly about anchorages and marinas than you ever will charging your batteries.
Mark
@ Foswick: Since diesels need compression heat to ignite the fuel, it has to have a full charge of air to generate enough heat at high load/RPM.. A gasoline engine at low load has the carburetor butterfly almost closed .. there is a vacuum in the cylinder ... and just enough air to burn the gasoline correctly.. ignited by a spark. The unthrottled intake is one of the things that makes a diesel more efficient.. Dr. Rudolf Diesel was pretty sharp and designed his engine taking advantage of thermodynamics to have it be efficient.. He made a big old pot full of money replacing coal burning steam engines on ships with his engine that could burn a wide variety of liquid fuels.. Interesting stuff.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,799
I am unclear as to the elements of cost attributed to solar making it cheaper.
Solar, if only the panels and the costs associated with attachment of the panels is being considered, then I agree the cost to set up a solar power generating system is inexpensive. But that is only a small part of the computation.
If you are going to produce some electricity, and you want to figure out the cost, you are going to add up some numbers:
1) What does the equipment cost?
2) How long will it last?
3) What are maintenance costs?
4) What other costs are involved in producing electricity (i.e. fuel)?
Of course, if you really want to get granular, you could estimate other costs such as what your time is worth and lost productivity costs, etc. if there are service disruptions. I'm not sure this would be an easy comparison because a) you don't need to take solar offline for maintenance except rarely, but b) you can run diesel at night. There are pros and cons in these margins.
But, we are just talking about how much does it cost to produce a kWh when you spread out all associated costs over a long period (often the useful life of the original equipment).
(I know I'm not telling you something you don't know - just walking you through my reasoning.)
I do not think that the case could be made that diesel is cheaper than solar by looking at those numbers except possibly in some fairly narrow circumstances and by narrowing the way you do the comparison.
For example, a diesel generator is capable of greater output for a given footprint. To match that with solar, you need a lot of panels. And, you might need to match that with considerable battery storage. But, we are no longer comparing production cost apples-to-apples, at that point. Now we are getting into usage profiles. In other words, that takes us into the realm of talking about whether a person can make one option or the other work more advantageously for their specific usage profile. That is a different discussion.
Similar to Maine Sail, our boat came equipped with an 8KW generator driven by a three cylinder Kubota diesel that runs governed at 1,800 RPM, which produces 60AH at 120V. Every other day, while out on our extended cruises, I run it for 1.5 hours to recharge our house bank, heat water and some cooking. During that time of heavy load the engine reaches operating temperature of around 190-200 degrees where it remains for the entire period. A bit silly to conclude that it never reaches operating temperature at that RPM.
What are the other parts of the computation for a solar power generating system? The initial cost to set up our solar has been the total cost (well, ignoring the tax break we got for it, which made solar cheaper than the initial cost). The only maintenance has been if a bird craps on them I need to hose it off. We've been operating solar for 23yrs, and hosing off bird crap is the only thing we've done in that time, but it didn't cost anything to do so.
Mark
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,799
I agree with the above statements about the cost to generate electricity, creation of a spark: solar vs generator. The solar panel purchase, associated wiring, and installation to create a spark extremely favors the Solar Panel over the generator. This is a limited context and only favors the SP during the daylight hours with adequate sunlight.
If we are attempting to answer this question in the OP, but substituting Solar for one of the identified generators, different context is involved than simply the cost to create a spark.
When I think about a boat generator the application is to provide electrical power 24/7. The elements of a System become more complex. To do a comparison involves the amount of energy desired to provide the power to run the systems when wanted/needed. I believe that the comparison in a boat application above the 30’th parallel would make the cost calculation about choosing a system much closer and may favor a small diesel generator over a solar system providing the same functions.
Solar power, just the sun, (even without running motors or lighting) is why such a large percentage of the world’s population survive without generators near the Equator. Solar does not work as well when you are north of the Fiftieth parallel. In this region the world population is pretty sparse without an auxiliary form of power.
Here's a video of Nigel talking about diesel auillaries and charging that begins to get a the low cost of using the diesel engine. Note, the savings is in the marginal costs associated with electrical generation with the auxiliary. Using the marginal costs is legitimate because the engine is already installed and running and a high output alternator is being used along with a smart regulator like the WakeSpeed or Zeus and one other new one.
Lower cost than a genset, but not cheaper than solar. However, solar requires real estate, where an alternator does not. Our HO alternator was $900, and a Zeus/Wakespeed another $900. Our 3kW of solar was $700 for the panels and $1200 for the controllers. So pretty much a wash, and both the engine and real estate were marginal costs for us, as they already existed. The only difference is it costs us $2.50/hr to operate the alternator if we aren't under propulsion, while the solar is always free.
They are complementary though, which is why we have both. The solar isn't very useful on rainy or cloudy days, but the solar generates far more energy over time, as the engine can't be run 12hrs/day when not being used for propulsion.
I am a proponent of HO alternators on small engines today, although maybe not as much as Calder. However, it still isn't a matter of just bolting one on and running with it, because cooling is a real issue with them. Even a Zeus/Wakespeed doesn't get you anything here, as they just dial back the output to keep the temperature in range. They make even more sense, and are way less expensive, if one can move to 48V.
Mark
They are complementary though, which is why we have both. The solar isn't very useful on rainy or cloudy days, but the solar generates far more energy over time, as the engine can't be run 12hrs/day when not being used for propulsion.
I am a proponent of HO alternators on small engines today, although maybe not as much as Calder. However, it still isn't a matter of just bolting one on and running with it, because cooling is a real issue with them. Even a Zeus/Wakespeed doesn't get you anything here, as they just dial back the output to keep the temperature in range. They make even more sense, and are way less expensive, if one can move to 48V.
Mark
The solution really depends on the sailing you do. Long term cruisers have different needs than weekend or summer vacation cruisers. If you are cruising on Lake Ontario, it really means you are motoring a lot, likewise on the ICW. In that case investing in getting every bit of energy out of the alternator makes a lot of sense. Off shore where sailing exceeds motoring more solar makes sense. And for many of us, a mix of both is the way to go.
Running a generator is probably the least efficient and cost effective and most annoying means of generating electricity. (Said as I listen to a neighboring boat's generator drone all day so the crew sit in an air conditioned cabin.)
Running a generator is probably the least efficient and cost effective and most annoying means of generating electricity. (Said as I listen to a neighboring boat's generator drone all day so the crew sit in an air conditioned cabin.)